diff --git a/Lib/decimal.py b/Lib/decimal.py
index fa41722..45ecf88 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -562,20 +562,46 @@
         # tuple/list conversion (possibly from as_tuple())
         if isinstance(value, (list,tuple)):
             if len(value) != 3:
-                raise ValueError('Invalid arguments')
-            if value[0] not in (0,1):
-                raise ValueError('Invalid sign')
-            for digit in value[1]:
-                if not isinstance(digit, (int,long)) or digit < 0:
-                    raise ValueError("The second value in the tuple must be "
-                                "composed of non negative integer elements.")
+                raise ValueError('Invalid tuple size in creation of Decimal '
+                                 'from list or tuple.  The list or tuple '
+                                 'should have exactly three elements.')
+            # process sign.  The isinstance test rejects floats
+            if not (isinstance(value[0], (int, long)) and value[0] in (0,1)):
+                raise ValueError("Invalid sign.  The first value in the tuple "
+                                 "should be an integer; either 0 for a "
+                                 "positive number or 1 for a negative number.")
             self._sign = value[0]
-            self._int  = tuple(value[1])
-            if value[2] in ('F','n','N'):
+            if value[2] == 'F':
+                # infinity: value[1] is ignored
+                self._int = (0,)
                 self._exp = value[2]
                 self._is_special = True
             else:
-                self._exp  = int(value[2])
+                # process and validate the digits in value[1]
+                digits = []
+                for digit in value[1]:
+                    if isinstance(digit, (int, long)) and 0 <= digit <= 9:
+                        # skip leading zeros
+                        if digits or digit != 0:
+                            digits.append(digit)
+                    else:
+                        raise ValueError("The second value in the tuple must "
+                                         "be composed of integers in the range "
+                                         "0 through 9.")
+                if value[2] in ('n', 'N'):
+                    # NaN: digits form the diagnostic
+                    self._int = tuple(digits)
+                    self._exp = value[2]
+                    self._is_special = True
+                elif isinstance(value[2], (int, long)):
+                    # finite number: digits give the coefficient
+                    self._int = tuple(digits or [0])
+                    self._exp = value[2]
+                    self._is_special = False
+                else:
+                    raise ValueError("The third value in the tuple must "
+                                     "be an integer, or one of the "
+                                     "strings 'F', 'n', 'N'.")
             return self
 
         if isinstance(value, float):
diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index e4b0ae5..27d1aa6 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -452,13 +452,18 @@
 
         #bad sign
         self.assertRaises(ValueError, Decimal, (8, (4, 3, 4, 9, 1), 2) )
+        self.assertRaises(ValueError, Decimal, (0., (4, 3, 4, 9, 1), 2) )
+        self.assertRaises(ValueError, Decimal, (Decimal(1), (4, 3, 4, 9, 1), 2))
 
         #bad exp
         self.assertRaises(ValueError, Decimal, (1, (4, 3, 4, 9, 1), 'wrong!') )
+        self.assertRaises(ValueError, Decimal, (1, (4, 3, 4, 9, 1), 0.) )
+        self.assertRaises(ValueError, Decimal, (1, (4, 3, 4, 9, 1), '1') )
 
         #bad coefficients
         self.assertRaises(ValueError, Decimal, (1, (4, 3, 4, None, 1), 2) )
         self.assertRaises(ValueError, Decimal, (1, (4, -3, 4, 9, 1), 2) )
+        self.assertRaises(ValueError, Decimal, (1, (4, 10, 4, 9, 1), 2) )
 
     def test_explicit_from_Decimal(self):
 
@@ -1060,6 +1065,28 @@
         d = Decimal("Infinity")
         self.assertEqual(d.as_tuple(), (0, (0,), 'F') )
 
+        #leading zeros in coefficient should be stripped
+        d = Decimal( (0, (0, 0, 4, 0, 5, 3, 4), -2) )
+        self.assertEqual(d.as_tuple(), (0, (4, 0, 5, 3, 4), -2) )
+        d = Decimal( (1, (0, 0, 0), 37) )
+        self.assertEqual(d.as_tuple(), (1, (0,), 37))
+        d = Decimal( (1, (), 37) )
+        self.assertEqual(d.as_tuple(), (1, (0,), 37))
+
+        #leading zeros in NaN diagnostic info should be stripped
+        d = Decimal( (0, (0, 0, 4, 0, 5, 3, 4), 'n') )
+        self.assertEqual(d.as_tuple(), (0, (4, 0, 5, 3, 4), 'n') )
+        d = Decimal( (1, (0, 0, 0), 'N') )
+        self.assertEqual(d.as_tuple(), (1, (), 'N') )
+        d = Decimal( (1, (), 'n') )
+        self.assertEqual(d.as_tuple(), (1, (), 'n') )
+
+        #coefficient in infinity should be ignored
+        d = Decimal( (0, (4, 5, 3, 4), 'F') )
+        self.assertEqual(d.as_tuple(), (0, (0,), 'F'))
+        d = Decimal( (1, (0, 2, 7, 1), 'F') )
+        self.assertEqual(d.as_tuple(), (1, (0,), 'F'))
+
     def test_immutability_operations(self):
         # Do operations and check that it didn't change change internal objects.