Adenine, adenosine, inosine, hypoxanthine, xanthosine, xanthine, guanine and guanosine blood levels in 11 Duchenne muscular dystrophy patients treated with allopurinol, 10 untreated patients and 8 healthy controls, were determined by HPLC. Serum ADA, PNP and 5′-NT were also determined. Untreated patients showed lower adenine (p<0.001) and higher adenosine, xanthine, ADA and PNP levels (p<0.01) than controls. Treated patients had lower adenine and higher xanthine levels (p<0.001), but higher hypoxanthine, xanthosine and guanine levels (p<0.001), than controls, with normal ADA and PNP. The changes observed in ADA and PNP levels suggest an involvement of these enzymes in accelerated degradation of purines in Duchenne dystrophy.