Nineteen depressed in-patients were studied in a follow-up design for 8 weeks or until discharge, using three depression scales and a hostility questionnaire. It was hypothesized within a cognitive theory of depression that, self-rated hostility being a measure of negative thoughts and attitudes, changes in hostility would precede mood changes. Analysis was by contemporaneous and cross-correlations between mood and hostility measures. High intercorrelations were obtained among the mood ratings which decreased significantly over time, as did two of the four hostility measures. The hypothesis was confirmed by the cross-correlations between nurses' mood ratings and intropunitiveness and direction of hostility. The cross-correlations with Beck and Hamilton scales supported the hypothesis at a non-significant level.