The objective of the study was to assess the feasibility of initiating daily peak flow monitoring in a research study of asthma in inner city children. We performed a descriptive study of patterns of peak flow monitoring in children randomized to receive a simple mini-Wright (SM) or an electronic recording meter (ERM). The ERM served as a "covert" meter, providing objective documentation of actual peak flow use. Sixty-five Hispanic or African-American children, ages 5-9 years, with a history of physician-diagnosed asthma participated in the study. All children resided in census tracts with 40% or more of the population living at or below the poverty level. Subjects were instructed to use a peak flow meter (the SM or ERM) at least twice daily over a 3 week period, and to record peak flow values in a paper diary. Subjects who received the ERM were not made aware that measurements were also recorded electronically. Differences in patterns of use of the SM and ERM were assessed with the Wilcoxon signed rank test and Wilcoxon sum rank test. Adherence to peak flow monitoring was evaluated by comparing the percent days with missing values in the manually completed diary with those obtained by computer record. The Friedman statistic was used to compare changes in compliance (percent of days with missing peak flow entries) over time. Accuracy of peak flow readings was assessed by comparing the manual and electronic recordings with paired and unpaired t-tests and with Pearson product moment correlations. The percent of days with missing peak flow entries on diaries increased from 1.4% to 10.6% from the first to third week of monitoring (P < 0.004). The ERMs indicated a significantly greater percent of missing data than did the manual records (P < 0.0002). The difference in the percent of missing data for the electronic and manual records was most notable during the third study week, when the ERM and the manually completed records indicated that 52% and 15% of days, respectively, were without peak flow measures. Large inter-subject variations in the relationship between manually and electronically recorded peak flow measurements were observed, suggesting that errors in reading and transcribing peak flow rates occur in a subset of asthmatics. We conclude that children and caretakers in the inner city may have considerable difficulty initiating and maintaining peak flow recordings. Data obtained by manual records may considerably overestimate actual use. Compliance with monitoring decreases markedly between the first and third week of monitoring.