Our study of a large canine population investigated whether the development of symptomatic canine leishmaniosis revealed any predilection for sex, age, or breed. Included in the study were 390 leishmaniosis-affected dogs that had been treated at the Hospital Clínic Veterinari attached to the Universitat Autònoma de Barcelona. Of the diseased dogs, 238 were male (61%) and 152 were females (39%), whereas percentages for males and females in the overall reference population of dogs treated at this unit were 53% and 47%, respectively, (P<0.05). Age distribution was bimodal, with the highest prevalence of the disease occurring at 2-4 years of age and a secondary peak occurring at seven years or over. The over represented breeds were the German shepherd (13.6% versus 6.35%, P<0.001), the Rottweiler (13.1% versus 3.0%, P<0.001), and the Boxer (7.9% versus 4.7%, P=0.002), whereas the underrepresented breeds were the Yorkshire terrier (0.5% versus 6.5%, P<0.001), and the Poodle (0.3% versus 3.0%, P<0.001).