An indirect immunofluorescence method using rat liver as material was developed to determine the incidence of antinuclear antibodies in serum from 44 adult dogs naturally infected with leishmaniasis and, for comparative purposes, in a control group of 30 healthy dogs. Animals in both groups were of different breeds with a similar age distribution. Antinuclear antibodies were not detected in the healthy dogs and only 15.9% of the diseased dogs, 12.0% males and 21.1% females, were positive. The results indicate that in contrast to previously reported figures, the incidence of antinuclear antibodies is low in canine leishmaniasis at least when diagnosis is first made. In order to investigate whether antinuclear antibodies may play a role in the development of the renal damage observed in canine leishmaniasis, the concentrations of serum creatinine were related to the presence of antinuclear antibodies. Only 28.5% of the antinuclear antibodies positive infected dogs showed hypercreatininemia as did 32.4% of the antinuclear antibodies negative infected dogs. Thus, antinuclear antibodies are not significantly cause-effect related to the development of the renal lesions seen in canine leishmaniasis.