An unusual monosymptomatic hypochondriacal delusion presenting as self-insertion of a foreign body into the urethra.

The case of a middle-aged man who inserted a knitting needle into his urethra is described. This behaviour was associated with a monosymptomatic hypochondriacal delusion. The causes of such behaviour are discussed, together with the nosological status of monosymptomatic hypochondriacal psychosis.