The purpose of the study is to examine the effect of PBL instruction on 12th grade students academic achievement, problem-solving skills and Self Directed Learning (SDL) in the unit of genetics and inheritance after controlling for students achievement level. Quasi experiment with non-equivalent control group, and pretest and posttest design was used for this study.The study concluded that PBL students appeared to be better compared to the conventional students in terms of academic achievement, problem-solving skills and SDL. The implication of the study suggested that PBL is seen effective...