A paperless electronic spirometer/diary instrument has been employed in a home monitoring programme for lung and heart-lung transplant patients at the University of Minnesota. The monitoring programme is part of a long term study to develop a system which will detect the earliest signs of developing rejection or infection in the transplanted organs. It is based on patient daily self-measurements of standard spirometry, vital signs, and symptoms recorded at home and transmitted weekly to the study data center over the telephone using a modem built into the instrument. This report summarizes adherence behaviour for 41 subjects enrolled in the study over a 12 month period. The number of subjects from whom home data has been received each week was used to measure adherence at the subject level. The number of records received each week measured adherence at the daily recording level. A data record consists of a daily set of spirometry, vital signs, and symptom values from a given subject. Approximately 82% of subjects transmitted records each week, over the 52 week review period. There was an average of 4.5 records received each week from each subject. Transmitted records had missing vital sign or symptom items in less than 2% of cases; spirometry data was always present. This evaluation showed that lung transplant recipients are willing and able to use a home-monitoring instrument, and that basic spirometry, data entry, and data transmission can be performed satisfactorily.