The study investigated and compared the effects of a transformation and a non-transformation approach to tenth grade geometry on retention of geometry and on transfer in eleventh grade mathematics. A geometry posttest, an advanced algebra pretest, a geometry retention test, an attitude inventory and an eleventh-grade mathematics achievement test were given to 184 eleventh grade students who had studied geometry by one of the two approaches the previous year. A multivariate analysis of regression and covariance were used to analyze the data. Findings indicated that transformation geometry resulted in greater retention of congruence, similarity, and symmetry, but no greater overall retention or transfer than with non-transformation geometry. (Author/DT)