Maximal inspiratory pressure (MIP) was assessed in 4,443 ambulatory participants of the Cardiovascular Health Study, 65 yr of age and older, sampled from four communities. Maximal expiratory pressure (MEP) was also measured in 790 participants from a single clinic. Positive predictors of MIP included male sex, FVC, handgrip strength, and higher levels of lean body mass (or low bioelectric resistance). Negative predictors were age, current smoking, self-reported fair to poor general health, and waist size. Both participant and technician learning effects were noted, but there was no independent effect of race, hypertension, cardiovascular disease, or diabetes. A healthy subgroup was identified by excluding current smokers, those with fair to poor general health, or an FEV1 less than 65% of predicted. Mean values determined from the healthy group were 57/116 cm H2O (MIP/MEP) for women, and 83/174 for men. Lower limits of the normal range (fifth percentiles) were 45 to 60% of the mean predicted values. The reference equations derived from this group of healthy 65 to 85-yr-olds may be used by pulmonary function laboratories and respiratory therapists who evaluate the respiratory muscle strength of elderly patients.