We used a simple quasiexperimental design to assess the efficacy of an inpatient cognitive-behavioral treatment program for persons with fibromyalgia syndrome (FS). Twenty-five participants were assessed on 3 occasions: (1) about 5 months before admission to the program, (2) on admission and (3) at discharge. In addition, the dependent variables (pain response measures) were divided into "target" (expected to change with treatment) and "nontarget" (not expected to change) to assess potential demand characteristics. Our results showed that, whereas no changes occurred in either target or nontarget variables between the initial assessment and admission, consistent changes were observed only in target variables between admission and discharge. Our data provide preliminary support for cognitive-behavioral treatment for FS.