There has been great interest in the night-to-night variability of sleep-disordered breathing because of the implications for the accuracy and costs associated with diagnostic testing. Night-to-night variability of sleep and respiratory parameters were examined in 66 older Whites and 56 older African Americans. Each participant had his or her sleep recorded for 2 nights with portable recording equipment. The correlations between the 2 nights were all large. Analyses of variance showed that men had a greater change in apnea index and in number of apneas than women. There were no differences in the parameters for African Americans versus Whites. One night of sleep recording may be sufficient for studying sleep disorders in elderly persons.