Seven adult cats were inoculated cutaneously at a shaved site with Microsporum canis; five (group A) had spontaneously recovered from a previous M canis infection, and two (group B) were dermatophyte-naive. Both of the dermatophyte-naive cats developed typical clinical disease, the lesions reaching maximal size four to five weeks after exposure, and resolving by week 13. Only one of the group A cats developed clinical disease; the lesions were more inflammatory in nature and of shorter duration and had resolved by day 25 after exposure. Blood samples collected from the seven cats before and four weeks after exposure were assessed for M canis-specific cellular (by lymphocyte proliferation assays) and humoral (by IgG and IgM ELISA) immune responses. After four weeks the group A cats had significantly (P < 0.05) increased cellular and IgG-humoral immune responses, and the group B cats also had increased cellular, and IgG and IgM responses but the increases were not significant.