The overall purpose of this research project was to examine the effects of prediction activities on instructional outcomes in a high school genetics unit. The researcher-developed prediction activities were designed to stimulate student interest and critical thinking prior to formal instruction on the concepts. Enhanced levels of classroom discussion and interaction, higher achievement motivation, positive attitudes toward science, and greater mastery of genetics concepts were identified as the areas of effectiveness being evaluated. Although the quantitative analyses showed no differences between the experimental and control groups, there were apparent qualitative differences. Students in the experimental treatment classes were described as displaying higher levels of interest and participation in the lesson. They were depicted as asking more thoughtful questions, and responding with interest to the challenges presented them while making and defending their predictions. (Author)