Few data are available about the muscle status in renal transplant recipients. Moreover, the list of myotoxic drugs is growing longer and some of them are likely to be prescribed in renal transplant patients. These conditions may act as confounding factors in case reports of both cyclosporin and colchicine myopathies. Moreover no study has evaluated the frequency of myopathy in patients on both colchicine and cyclosporin. We conducted a retrospective study including all renal transplant recipients followed in our unit in whom colchicine was prescribed since January 1994. Clinical and biological data of patients on both colchicine and cyclosporin were analysed. Secondly case subjects were compared with matched controls not receiving colchicine but cyclosporin. Ten patients received colchicine in association with cyclosporin. Five patients (50%) experienced muscular symptoms and when performed, muscular histology showed vacuolar myopathy. All five patients improved after colchicine withdrawal. Cases with and without muscular symptoms did not differ in age, transplant duration, and serum creatinine level. Mean duration of colchicine therapy was 12.2 +/- 4.4 months in cases with muscular symptoms and 6.8 +/- 4.6 months in cases without muscular symptoms (P < 0.05). No control complained of either muscular pain nor weakness (P < 0.0005). Only one patient (3.3%) had elevated serum creatine phosphokinase concentration (P < 0.0005). We conclude that myopathy is very frequent in patient on both colchicine and cyclosporin. Muscular symptoms improve in all patients after colchicine withdrawal.