Good premorbid (GP) schizophrenics have been found to have higher word association commonality scores than poor premorbid (PP) schizophrenics when both groups had been hospitalized over 5 years but not with shorter hospitalizations. There has been no previous study of changes in commonality in schizophrenics from beginning to end of hospitalization. The present study was a longitudinal investigation of word association commonality in GP and PP schizophrenics from admission to discharge from the hospital and at 3-month follow-up. Subjects were 16 GP and 16 PP schizophrenics. The two groups were equal in age, education, intelligence, and length of hospitalization. Commonality scores consisted of number of common responses to 50 Kent-Rosanoff stimulus words. GP and PP groups were not significantly different in commonality at admission, discharge, or follow-up. The combined groups showed a significant (p less than .01) increase in commonality from admission to discharge but no further change from discharge to follow-up. Taken separately, the GP group showed a significant increase in commonality from admission to discharge (p less than .02), while the PP difference was not statistically significant. The change in the GP group was significantly greater than in the PP group (p less than .05, one-tailed test). These results suggest that schizophrenics' word association commonalities may increase with improvement in clinical status and that GP schizophrenics show greater increases than PP schizophrenics.