The clinical histories of two patients with quariceps contracture seen within the last one year have been analysed and a search has been made particularly for a common cause. Study of our two patients revealed that they had all had injections into the thigh after birth for serious illness. The objects of this paper are to suggest that an important factor in the etiology of the quadiceps muscle is the giving of intramuscular injections into the thighs. The muscles into which these intramuscular injections and subcutaneous infusions have been given are often the site of considerable edema and hemorrhage. The occasional development of firbrosis followed by contractue afterr months or years is thought to be a reasonable possibility. It seems thus to be a typical iatrogenic lesion. The most striking elinical feature is the definite block to flexion at a variable angle association with firm mass, dimple and puckered scar. If slight contracture develop this thigh must be abandoned for further injections. Physiotherapy is started immed iately to try to overcome the developing extension contraeture. In established contracture surgical interevention gives good result. The appearance of cases of this sort only during the last years may be related to the ever increasing frequency of administration of ever more potent antibiotics into the quadriceps muscle.