The mitochondrial changes were studied, using transmission electron microscope, during hind limb regeneration in a larval stage (number 53) of the Egyptian toad, Bufo regularis Reuss at intervals, one, three five and seven days after amputation at the prospective knee joint level. Mitochondria were found in both control and experimental animals having different forms, sizes and positions. Cristae were noticed obviously extended reflecting continuous metabolic activities. Large electron dense granular masses were observed within the mitochondrial matrix in both control and experimental animals during the first five days after amputation. These granules decrease in later stages. It is suggested that mitochondria are active during different stages of regeneration. The variations in form, size and position of mitochondria might be related to its functional performance. The electron dense masses are suggested to be storage material and are consumed during cellular growth in the early phases of regeneration.