The authors investigated the comparative effect of the learning cycle and expository instruction on 8th-grade students' achievement in genetics. They adopted the nonequivalent control group design as a type of quasiexperimental design. The experimental group (N = 104) received learning cycle instruction, and the control group (N = 109) received expository instruction. The 2-way analysis of covariance indicated a statistically significant posttreatment difference between the experimental and control groups in favor of the experimental group after instruction. Results also revealed that students' logical thinking ability and meaningful learning orientation accounted for a significant portion of variation in genetics achievement. However, the authors found no statistically significant difference between girls' and boys' performance with respect to genetics achievement.