Although costly polysomnography (PSG) is not routinely performed with people with insomnia, it may be more necessary with recruited older adults with insomnia because this population may pose a greater risk of veiled sleep disorders compared with younger age groups and with referred samples. The present PSG screening of a recruited sample of older adults with insomnia found a 29%-43% rate of undiagnosed sleep apnea (SA), depending on whether an apnea-hypopnea index of 15 or 5 was used, after interviews had already screened out obvious cases of SA. Also, PSGs revealed a 4% rate of occult periodic limb movements. A discriminant analysis identified overweight men reporting dry mouth at highest risk for occult SA, with an apnea-versus-insomnia classification success rate of 78%. Using PSG evaluations in research on insomnia in recruited older adults is requisite to preclude substantial representation of occult SA.