diff --git a/src/function/builtin/GREATERP.java b/src/function/builtin/GREATERP.java
index 974107f..850626d 100644
--- a/src/function/builtin/GREATERP.java
+++ b/src/function/builtin/GREATERP.java
@@ -8,8 +8,8 @@ public class GREATERP extends LispFunction {
     private ArgumentValidator argumentValidator;
 
     public GREATERP() {
-        this.argumentValidator = new ArgumentValidator("GREATERP");
-        this.argumentValidator.setMinimumNumberOfArguments(2);
+        this.argumentValidator = new ArgumentValidator(">");
+        this.argumentValidator.setMinimumNumberOfArguments(1);
         this.argumentValidator.setEveryArgumentExpectedType(LispNumber.class);
     }
 
diff --git a/src/function/builtin/LESSP.java b/src/function/builtin/LESSP.java
index 82c3ade..5024649 100644
--- a/src/function/builtin/LESSP.java
+++ b/src/function/builtin/LESSP.java
@@ -1,49 +1,43 @@
 package function.builtin;
 
-import function.LispFunction;
+import function.*;
 import sexpression.*;
 
-/**
- * <code>LESSP</code> represents the '&lt;' function in Lisp.
- */
 public class LESSP extends LispFunction {
 
-    public SExpression call(Cons argList) {
-        // make sure we have received at least one argument
-        if (argList.nullp()) {
-            Cons originalSExpr = new Cons(new Symbol("<"), argList);
+    private ArgumentValidator argumentValidator;
 
-            throw new RuntimeException("too few arguments given to <: " + originalSExpr);
-        }
+    public LESSP() {
+        this.argumentValidator = new ArgumentValidator("<");
+        this.argumentValidator.setMinimumNumberOfArguments(1);
+        this.argumentValidator.setEveryArgumentExpectedType(LispNumber.class);
+    }
 
-        SExpression firstArg = argList.getCar();
-        Cons argRest = (Cons) argList.getCdr();
+    public SExpression call(Cons argumentList) {
+        argumentValidator.validate(argumentList);
 
-        // make sure that the first argument is a number
-        if (firstArg.numberp()) {
-            LispNumber num1 = (LispNumber) firstArg;
+        return callTailRecursive(argumentList);
+    }
 
-            if (argRest.nullp()) {
-                return Symbol.T;
-            }
+    private SExpression callTailRecursive(Cons argumentList) {
+        Cons remainingArguments = (Cons) argumentList.getCdr();
 
-            SExpression secondArg = argRest.getCar();
+        if (remainingArguments.nullp())
+            return Symbol.T;
 
-            // make sure that the second argument is a number as well
-            if (secondArg.numberp()) {
-                LispNumber num2 = (LispNumber) secondArg;
+        SExpression firstArgument = argumentList.getCar();
+        SExpression secondArgument = remainingArguments.getCar();
+        LispNumber number1 = (LispNumber) firstArgument;
+        LispNumber number2 = (LispNumber) secondArgument;
 
-                if (num1.getValue().compareTo(num2.getValue()) < 0) {
-                    return call(argRest);
-                }
+        if (!isFirstLesser(number1, number2))
+            return Nil.getInstance();
 
-                return Nil.getInstance();
-            }
+        return callTailRecursive(remainingArguments);
+    }
 
-            throw new RuntimeException("<: " + secondArg + " is not a number");
-        }
-
-        throw new RuntimeException("<: " + firstArg + " is not a number");
+    private boolean isFirstLesser(LispNumber number1, LispNumber number2) {
+        return number1.getValue().compareTo(number2.getValue()) < 0;
     }
 
 }
diff --git a/test/function/builtin/GREATERPTester.java b/test/function/builtin/GREATERPTester.java
index 9de0446..9e2d8d3 100644
--- a/test/function/builtin/GREATERPTester.java
+++ b/test/function/builtin/GREATERPTester.java
@@ -8,6 +8,13 @@ import function.ArgumentValidator.*;
 
 public class GREATERPTester {
 
+    @Test
+    public void testGreaterpWithOneNumber_ReturnsT() {
+        String input = "(> 1)";
+
+        assertSExpressionsMatch(evaluateString(input), parseString("t"));
+    }
+
     @Test
     public void testGreaterpWithTwoNumbers_ReturnsNil() {
         String input = "(> 1 2)";
@@ -43,7 +50,7 @@ public class GREATERPTester {
 
     @Test(expected = TooFewArgumentsException.class)
     public void testGreaterpWithTooFewArguments() {
-        evaluateString("(> 1)");
+        evaluateString("(>)");
     }
 
 }
diff --git a/test/function/builtin/LESSPTester.java b/test/function/builtin/LESSPTester.java
new file mode 100644
index 0000000..21f4201
--- /dev/null
+++ b/test/function/builtin/LESSPTester.java
@@ -0,0 +1,56 @@
+package function.builtin;
+
+import static testutil.TestUtilities.*;
+
+import org.junit.Test;
+
+import function.ArgumentValidator.*;
+
+public class LESSPTester {
+
+    @Test
+    public void testLesspWithOneNumber_ReturnsT() {
+        String input = "(< 1)";
+
+        assertSExpressionsMatch(evaluateString(input), parseString("t"));
+    }
+
+    @Test
+    public void testLesspWithTwoNumbers_ReturnsNil() {
+        String input = "(< 2 1)";
+
+        assertSExpressionsMatch(evaluateString(input), parseString("nil"));
+    }
+
+    @Test
+    public void testLesspWithTwoNumbers_ReturnsT() {
+        String input = "(< 2 3)";
+
+        assertSExpressionsMatch(evaluateString(input), parseString("t"));
+    }
+
+    @Test
+    public void testLesspWithManyNumbers_ReturnsNil() {
+        String input = "(< 4 3 2 5 1)";
+
+        assertSExpressionsMatch(evaluateString(input), parseString("nil"));
+    }
+
+    @Test
+    public void testLesspWithManyNumbers_ReturnsT() {
+        String input = "(< 0 1 2 3 4)";
+
+        assertSExpressionsMatch(evaluateString(input), parseString("t"));
+    }
+
+    @Test(expected = BadArgumentTypeException.class)
+    public void testLesspWithNonNumbers() {
+        evaluateString("(< '(1) '(2))");
+    }
+
+    @Test(expected = TooFewArgumentsException.class)
+    public void testLesspWithTooFewArguments() {
+        evaluateString("(<)");
+    }
+
+}