An experimental home monitoring system for assessing the progress and planning changes in the care of patients with cystic fibrosis (CF) has been implemented at the University of Minnesota Cystic Fibrosis Center. One group of patients and families did daily recording of physical measurements and symptoms, and sent the diary to the data coordinating center weekly for analysis. The remaining patients were not part of the home monitoring program. Twenty-five patients were randomly selected from the home monitoring group. They were compared to an age- and sex-matched control group not doing home monitoring to ascertain if home self-measurement and daily diary recording, in the absence of any therapeutic intervention, produced any change in physical or psychological status, pulmonary function, or growth over a 4-year study period. Subjects ranged in age from 6 to 43 years. Clinical status was measured by the National Institutes of Health cystic fibrosis scoring system. Pulmonary function was assessed as percent of predicted forced vital capacity and percent of predicted forced expiratory volume in 1 sec (FEV1). Growth was analyzed as percent of predicted weight based on age-, sex-, and height-dependent equations. Psychological status was determined by self-assessment and referral for conseling. Only percent predicted FEV1 in the control group declined significantly. There were no statistically significant changes in any other measures either within or between diary and nondiary groups over the 4-year period.(ABSTRACT TRUNCATED AT 250 WORDS)