The changes in the titres of anti-leishmania antibodies in 25 dogs with leishmaniasis were studied by using a Dot-ELISA technique while they were being treated with N-methylglucamine and allopurinol. When the diagnosis of leishmaniasis was established, 21 of the dogs had positive titres (1:800 or higher), and after treatment, 15 of them still had high titres, in most cases the same as at the point of the diagnosis. In four dogs the titres decreased, and were less than the cut-off value in two cases nine months after treatment. Only four dogs had titres less than the cut-off value when they were diagnosed, but one month later the titres in all four dogs had reached the cut-off value. There was no correlation between the serological titres and the severity of the clinical signs. It is concluded that the Dot-ELISA is a sensitive method for the diagnosis of canine leishmaniasis but is not satisfactory for monitoring the clinical development of the disease.