A language
L has a property tester if there exists a probabilistic algorithm that given an input
x queries only a small number of bits of
x and distinguishes the cases as to whether
x is in
L and
x has large Hamming distance from all
y in
L. We define a similar notion of quantum property testing and show that there exist languages with good quantum property testers but no good classical testers. We also show there exist languages which require a large number of queries even for quantumly testing.