Thirteen dogs with nictitans plasmocytic conjunctivitis were treated with 2.0 per cent cyclosporin drops in the right eye and with 0.1 per cent dexamethasone ointment in the left eye. The response to both therapies was monitored for six weeks, repeat biopsy specimens were taken, and the time for the clinical signs to recur recorded. Conjunctival cultures were taken before and after both therapies. There were no significant differences between the treatments in the remission of clinical signs, the reduction of inflammatory infiltrate in the biopsy specimens, or the time to recurrence of the condition or its subsequent severity. However, the eyes treated with 0.1 per cent dexamethasone tended to recover more rapidly than the eyes treated with 2.0 per cent cyclosporin, and the eyes treated with 2.0 per cent cyclosporin tended to be protected from a recurrence for longer than the eyes treated with 0.1 per cent dexamethasone.