Reports of accessory soleus muscle are rare, perhaps as a result of it often remaining unrecognized. It presents as a swelling behind the ankle and may be mistaken for a tumour or inflammatory lesion, as occurred in the first of a series of three cases. The other two were incidental findings, one in a 30 year old man with an open tibial fracture and the other in a 9 month old child with a club foot. Patients present with either pain or a diagnostic problem. When large, it may make wearing of footwear difficult. Computerized tomography with electromyography enables confirmation of the diagnosis. Pain is relieved by epimysiotomy and when encountered incidentally during surgery, incision of the epimysium is all that is needed. Excision of the muscle may be considered only if wearing of footwear is difficult. The significance of its presence in a case of club foot is unknown. Disinsertion of its insertion was all that was required to obtain surgical correction of the deformity in the present case. Awareness of the condition will prevent unnecessary surgery in asymptomatic cases.