Previous studies have shown a decreased progression of the course in Duchenne muscular dystrophy (DMD) patients treated by lower limb surgery in early childhood. The use of 3-methylhistidine (3-MH) excretion and 3-MH/creatinine excretion ratio as an appropriate indicator for the myofibrillar protein catabolic rate (MPCR) in muscle disorders is discussed controversially. To explore this issue we studied the renal excretion of (3-MH) over a period up to 24 months (on average 20.8 +/- 1.4) after operation in 15 consecutive DMD patients with an average age at operation of 8.75 (+/- 2.43 years) to evaluate the myofibrillar protein catabolic rate. No significant change of the MPCR could be found in our population over the follow-up period. However, the formula for the calculation of the MPCR contains quantities which are not precisely known in DMD or assumed to be constant over the progressive course of DMD. Summarizing MPCR cannot be recommended for the assessment of therapeutic efficacy in DMD.