Two patients with tendinitis by ciprofloxacin are described. In both patients isolated involvement of the Aquilles tendon was produced. The symptoms initiated at 2 to 4 weeks of the beginning of treatment. The two patients had undergone chemotherapy and bone marrow transplantation due to chronic myeloid leukemia and acute promyelocytic leukemia, respectively with no data on recurrence of leukemia being obtained at the time of the tendinitis. Suppression of ciprofloxacin achieved disappearance of the symptomatology.