Following up on earlier studies, the study reported in this paper further examined analogy as a source of interference to learning. Subjects, 103 undergraduate students randomly divided into three groups, studied a passage on Manichaeism with the aid of one of three forms of study guides: one having students generate comparisons between Manichaeism and Christianity, one having students generate contrasts, and one having students generate information about Manichaeism without reference to Christianity. Learning was measured with a free-recall test followed by a 20-item multiple choice test on Manichaeism. Results indicated that subjects who studied the text with a study guide requiring students to generate comparisons between the religions scored lower, recalled fewer correct facts, and gave significantly more incorrect information than students in the other two treatment groups. Findings lend support to earlier studies that found that analogies can enhance the effectiveness of study guides if the analogies do not compete with analogies in material to be learned. (One table of data is included; 23 references are attached.) (RS)