The purposes of this study were to develop interactive journal writing activities, to study students writing ability and to compare students motivation in writing before and after being taught with interactive journal writing activities. The subjects were 45 students who took reading-writing course in the first semester of the 1998 academic year at Nawamindhrachudhit Payap School, Maerim District, Chiang Mai. The research instrument consisted of 8 lesson plans via interactive journal writing activities, evaluative forms of activity effectiveness, a writing ability test and a motivational questionnaire. The motivational questionnaire was administered to survey the students motivation in writing before the experiment. After the 12- week experiment, the students writing ability was assessed, and students motivation in writing was investigated again. The data obtained were analyzed by using mean, percentage, standard deviation and paired-t-test. The findings revealed that interactive journal writing activities were effectively developed for enhancing writing skills and motivation and that students writing ability was highly satisfactory. In addition, the students motivation in writing was significantly higher than prior to the experiment at the level of .001.