The authors discuss a case of human leptospirosis, caused by Leptospira canicola, having the etiological agent been isolated by hemoculture on the fifth day of Clinical evolution. The disease's chief manifestations were fever and intense headache, besides myalgia and repeated vomiting. Symptoms appeared suddenly; while signs of meningeal involvement were lacking, there were indications of renal implications. Jaundice has not been observed during the course of the disease and the cure was attained within a reasonably short time. The authors stress this as the first Brazilian case where the responsible spirachaeta-precisely Leptospira canicola - could be isolated and duly identifield.