This study examined the effects of in-class writing to learn mathematics on college students in a college algebra course. The students in the two experimental groups wrote explanatory responses to prompts regarding a topic discussed in class the previous day twice a week for eight weeks. The teacher read and responded to all writing assignments the next day. The two control groups spent the time discussing additional examples as a class. All other aspects of the course were held constant for the 209 students in the study;The first goal of the study was to investigate the effect of the in-class writing on mathematics achievement. The second goal was to investigate the effect of the in-class writing on the students' attitude toward Mathematics; A third goal was to investigate whether the in-class writing treatment would be differentially effective for some students more than others based on previous mathematics achievement, length of time since the last math class, or self reported study habits;Findings of the study showed that the in-class writing treatment was differentially effective on the attitudes of low achievement students. The low achievement writing students had significantly more positive attitudes toward mathematics at the end of the study than the low achievement nonwriting students. Also there was a significant interaction for the treatment x time since the last mathematics class. The students in the writing group who had not taken a math class for 1.5 years or more had significantly better achievement scores than those in the control group who had not recently completed a math course. These two findings may have practical implications for making mathematics accessible to more students through the use of writing assignments. In general, the study did not find a significant effect for either attitude or achievement for the writing groups.