Dietary self-monitoring is considered the core of behavioral weight control programs. As software for personal digital assistants (PDA) has become more available, this study investigated whether the use of a PDA would improve dietary self-monitoring frequency and subsequent weight loss over the use of traditional paper diaries. One-hundred-seventy-six adults (BMI 25-39.9) participated in a 6-month behavioral weight control program. Treatment subjects (n = 61) were provided with a PalmZire 21 with Calorie King's Diet Diary software installed. Their self-monitoring habits and weight loss were compared with the results from a previous program (n = 115) which followed the same protocol using paper diaries for self-monitoring. No significant differences in weight loss or dietary self-monitoring were found. More frequent self-monitoring correlated with weight loss in both groups (p<.001). People seeking to lose weight should be encouraged to self-monitor and be matched with a mode of self-monitoring that is fitting to their lifestyle and skills.