The Solomon four-group design (R. Solomon, 1949) is a very useful experimental design to investigate the main effect of a pretest and the interaction of pretest and treatment. Although the design was proposed half a century ago, no proper data analysis techniques have been available. This paper describes how data from the Solomon four-group design can be analyzed properly using maximum likelihood regression analysis. The results show that both the parameter estimators and the expressions for the standard errors are in agreement with related designs and with intuitive expectations. (Author/SLD)