The factorial invariance of student ratings of in struction across three curricular areas was investi gated by means of maximum likelihood factor analysis. The results indicate that a one-factor model was not completely adequate from a statisti cal point of view. Nevertheless, a single factor was accepted as reasonable from a practical point of view. It was concluded that the single factor was in variant across three curricular groups. The reliabil ity of the single factor was essentially the same in the three groups, but in every case it was very high. Some of the theoretical and practical implications of the study were discussed. © 1981, Sage Publications. All rights reserved.