A summation model of classical conditioning was used to describe the deviant sexual arousal pattern of a male psychiatric patient. Penile assessment showed a response to a compound stimulus (radio static plus a picture of a woman) that was approximately equal to the sum of the responses to each component alone. The subject's self-report of sexual arousal followed a similar pattern. A distinction was made between total and partial fetishism. It was suggested that what may be particularly troublesome in partial fetishism is the potential for high levels of summated arousal.