In April 1995, centre received a request from the collector and chief medical officer of Mandla district to investigate the cause of a mysterious disease characterized by pain and deformity (Genu valgum) in the lower limbs, mostly among children and adolescents below age 20 in two villages of the district. Thus this epidemiological investigation was undertaken with the objective to find the cause of the knock-knee deformity. The investigation was carried out in two affected villages of Mandla district. The first village was Tilaipani, located about 12 km east of the district headquarter Mandla; the second village was Hirapur, which was about 50 km southwest of Mandla City. Tilaipani had a population of 542 in various age groups, and Hirapur had about 620. Evaluation of data comprised of obtaining and recording of medical histories, detailed clinical and radiological examinations, examination of biochemical parameters of blood, fluoride levels in urine and in all drinking water sources and dietary surveys. Biochemical investigations included serum alkaline phosphatase, inorganic phosphorus and serum calcium. Dietary surveys were conducted using the 24-hr recall method. Fluoride levels were estimated using a fluoride ion selective electrode.