Report of two adult males, 31 and 24 years-old, with hypertrophy in their left inferior limb, with denervation in the electromyography. Both patients undergone to a muscle biopsy in the normal and in the enlarged limb, which were processed by histochemistry. The mean muscle fiber diameter, percentage of muscle type fibers and atrophy and hypertrophy factors were calculated, as well as histographic fiber analysis. We found rare atrophic muscle fibers and one of the patients had hypertrophy of type II muscle fiber and the other hypertrophy of both types. The calculation of the atrophy and hypertrophy factors, revealed a predominance of type II fiber hypertrophy in both quadriceps of the two patients and type I hypertrophy in one case. A discussion about the factor responsible by the hypertrophy in denervation is made. The possible etiology of one case was a SI radiculopathy and in the other, a possible motor neuron disease.