Recent studies have suggested that requiring written responses as part of programed instruction format may have a negative effect on learning while more difficult responses may have the effect of holding interest and increasing achievement. To further explore the effect of response mode on rates of learning, a study was designed which compared the effects of: overt response; optional response; covert response; and implicit (reading) response. Four programed booklets, one representing each response mode were prepared and administered randomly in two eighth grade classrooms. Pre- and posttests were used to assess amount learned and records were kept for time required to complete lesson. A learning efficiency index was calculated, and the implicit reading response mode proved the most efficient. (EMH)