A baseline survey of ventilatory function was performed using spirometry. PEF was measured daily with a mini-Wright Peak Flow Meter over a period of several weeks in a study of 201 normals (staff, faculty and graduate students at the University of Massachusetts Lowell). Serial PEF data were collected on a group of mild asthmatics identified in a local occupational medicine clinic. Finally, performance characteristics were examined in serial PEF data from two existing occupational cohort studies.