Evaluation of the change in performance on the Blessed Memory Information Concentration Test over a one-year period was used as a probe for the prevalence of reversible cognitive disorders among patients living in a residential care facility. Of 157 patients with cognitive impairment at the initial assessment, 10 (6.4%) improved by 6 points or more, 19 (12.1%) improved by 5 points or more, and 15 (9.6%) had a reduction in the number of errors by 33% or more. Thus, using improvement over time as an indicator, we estimate that 6% to 12% of the elderly patients in our sample had a reversible component to their cognitive impairment at the initial assessment. Retrospective review of medical records identified (one or more) possible causes for impairment at baseline in each of the ten patients who showed the greatest improvement: adverse drug effects in seven patients, depression in two, and metabolic encephalopathies in three.