In the autumn two patients with general malaise were consecutively admitted to the department of internal medicine of our hospital in the northern region of Nagasaki Prefecture. Since both patients were engaged in rice farm work and showed conjunctival suffusion and pain of the gastrocnemius muscle, leptospirosis was suspected. The first patient required temporary hemodialysis for renal dysfunction, whereas liver dysfunction developed in the second patient. The disease was remitted by antimicrobial agents. A diagnosis of leptospirosis was made serologically in both patients. Leptospirosis should be considered as a differential diagnosis when a patient engaged in farm work in the autumn has typical symptoms, and an early initiation of treatment after onset is important.