The purpose of this study was to assess the psychometric properties of the newly developed Impact of Weight Loss Scale (IWLS), a subjective measure of perceived weight loss and related behaviour, body image perception, and affect, as well as the scale's relationship to mental health and nutritional measures in an HIV sample. Seventy-five HIV-positive men were administered the IWLS along with measures of depression, quality of life and nutritional status. Half (51%) of the sample had a CD4 count below 200 cells/cu.mm, and 80% had significant loss of body weight (> or = 10% body weight loss) or body cell mass (< or = 90% of normative body cell mass). The IWLS demonstrated good internal consistency reliability (Cronbach's alpha = 0.88) and had a unidimensional factor structure. Higher IWLS scores, which indicate a more detrimental impact of weight loss, were correlated with greater depression (r = 0.29), reduced quality of life (r = -0.37), and objective nutritional deficits (ratio of body cell mass/height, r = -0.28; amount of weight loss, r = 0.30). The IWLS is a brief self-report measure with good psychometric characteristics and has potential utility in both research and clinical applications.