OBJECTIVES: This pilot study compared a prototype electronic menstrual calendar on a handheld computer with a paper calendar for data quality and participants' perceptions.

DESIGN: Twenty-three women completed identical information about menstrual bleeding and symptoms using paper and electronic calendars for 1 month each.

RESULTS: Use of the paper calendar resulted in more missing data than the electronic calendar for bleeding characteristics (13% vs. 4%) and symptoms (35% vs. 4%). The electronic calendar's ability to log data entries revealed retrospective entry for 61% of the data. Total data entry and cleaning time was reduced by 81% with the electronic calendar. Overall, participants preferred the electronic (70%) to the paper (22%) calendar.

CONCLUSIONS: Data quality with conventional paper calendars may be poorer than recognized. The data-logging feature, unique to the electronic calendar, is critical for assessing data quality. Electronic menstrual calendars can be useful data collection tools for research in women's health.