Functional explanations are regarded as a special type of explanation by many biologists. Philosophers of science tend to agree that they are weak forms of the common modes of explanation, although the elucidation of the logical structure involved is difficult. The present paper shows that Hempel's reconstruction of functional explanations is inadequate on pragmatic grounds. Thus his conclusion that such explanations are necessarily weak is also objectionable. There is no reason for allotting functional explanations a special logical status.