Evidence regarding how health information technologies influence clinical work patterns and support efficient practices is limited. Traditional paper-based data collection methods are unable to capture clinical work complexity and communication patterns. Our objective was to design and test an electronic data collection tool for work measurement studies which would allow efficient, accurate and reliable data collection, and capture work complexity. We developed software on a personal digital assistant (PDA) which captures details of nurses' work; what task, with whom, and with what; multi-tasking; interruptions and event duration. During field-testing over seven months across four hospital wards, fifty-two nurses were observed for 250 hours. Inter-rater reliability scores were maintained at over 85%. Only 1% of tasks did not match the classification developed. Over 40% of nurses' time was spent in direct care or professional communication, with 11.8% in multi-tasking. Nurses were interrupted approximately every 49 minutes. One quarter of interruptions occurred while nurses were preparing or administering medications. This approach produces data which provides greater insights into patterns of clinician's work than has previously been possible.