This retrospective study of impairments in a decentralized and integrated, routine Hansen's disease (HD) programme was done on a cohort of all new patients detected in Rondônia state from 1996 to 1999. It shows that the dynamics of impairments during treatment in Rondônia are similar to what has been published in other recent studies from Africa and Asia. Data about impairments at detection and at release from treatment (cure), the prescription of steroids, and epidemiological information are provided. Of the original 5350 new patients, 4230 patients (80%) completed multidrug therapy (MDT) and had complete data about their impairment status. At the start of treatment, 9% of the paucibacillary (PB) and 26% of the multibacillary (MB) patients had WHO grade 1 impairment. Three percent of the PB and 11% of the MB patients had visible deformities (WHO grade 2 impairment). Of the patients without impairments (grade 0) at the start of treatment, 5% of the PB and 20% of the MB patients developed impairments during treatment. Of the PB patients with a WHO impairment grade 1 at start of treatment, 34% improved and 6% got worse. Of the MB patients 34% improved and 12% became worse. In a separate study of patients from the 1997 intake, 17% of the PB and 58% of the MB patients were treated at least once with a course of steroids or thalidomide during MDT treatment. It is noted in the literature that the percentage of persons with recent nerve function impairment (NFI), nerve pain or tenderness and/or reaction reactions differs between projects. This may reflect real differences or may be caused by differences in routine monitoring and/or criteria and methods of treatment. The use of the WHO maximum score, particularly for the patients with grade 2, is not as sensitive to change as utilizing the summary of Eye, Hand and Foot (EHF) scores. If overall impairment figures are given, the proportions of MB patients may define the differences between projects, therefore it is important to analysis and present the results of PB and MB patients separately. The most simple (outcome) indicator to estimate the effectiveness of patient management would be the proportions of patients with impairment grade 0 at start of treatment who develop either grade 1 or 2 impairments during treatment. An additional (outcome) indicator could be the proportion of patients with impairment grade 1 at start of treatment who develop grade 2 impairments during treatment. Currently, no operational targets or acceptable level of performance for patient management have been set. This would be important to enable programme managers to determine if adequate patient education, treatment and follow up have been provided after the disease detection to prevent and/or minimize problems associated with the disease. The available evidence strongly suggests that reactions and impairments related to HD will continue to occur in large numbers, requiring the development of adequate infrastructures and sustainable services to detect and to manage problems associated with HD during and after MDT treatment.