Ingrowing of the nail of the hallux has been ascribed to an abnormality of the shape of the nail; our prospective study was planned to test this association. Twenty-three consecutive patients and 23 age-matched controls were assessed by caliper measurement and standard photographs, before a first operation for ingrowing toenail. We found no differences in shape between the toenails of the patients and those of the controls, both groups showing great variation. Our results suggest that the ingrowth is not commonly associated with an abnormal shape of the nail.