This paper examines the extent of nerve thickening among leprosy patients detected in the field in Agra district. All the clinically diagnosed leprosy patients were examined in detailed for thickening of local cutaneous nerves and peripheral nerve trunks. In each case all the major nerve trunks in both upper and lower extremities, forehead and neck were examined for thickening. Nerve thickening was found in 94% of multibacillary (MB) patients and among 52% paucibacillary (PB) patients. Nerve thickening was found to be more in males, in prevalent cases than in new (untreated) cases and increased significantly with age and delay in diagnosis (P<0.001). Visible deformities of grade > or =2 were found in 10% (58/573) of the leprosy patients; paralytic deformity accounted for 78% (45/58). Claw hand alone or in combination was seen in 82% (37/45) of patients with paralytic deformities. Risk (odd ratio) for deformities was observed to be high (15-18 times) with increasing number of nerves among patients with neuritic leprosy but correlated with delay in diagnosis of over 5 years. Likewise, deformities were more often seen in those with skin lesions, provided they had > or =3 thickened nerves. Findings suggest that early detection and treatment is useful in preventing deformities.