Many laboratory polysomnographic (LPSG) studies have shown only modest sleep differences between insomniacs and matched, noncomplaining normal controls. However, the extent to which LPSG methodology affects the outcome of such comparisons has yet to be tested. In the current investigation, 32 (16 females, 16 males) older (age > or = 60 years) insomniacs and an age-matched and gender-matched sample of 32 noncomplaining normal sleepers underwent three consecutive nights of LPSG monitoring and another three consecutive nights of PSG monitoring in their homes (HPSG). By random assignment, one-half of the subjects in each group underwent LPSG first, whereas the remaining subjects underwent HPSG first. Each PSG recording was blindly scored using conventional scoring criteria, and resulting measures of total sleep period, total sleep time, sleep efficiency percent, stage 1 time, slow-wave sleep time, and rapid eye movement latency were used to compare the two subject groups within each PSG recording site (i.e. lab and home). Statistical analyses showed the normals sleepers and insomniacs evidenced similar pronounced first night effects (FNEs) when undergoing LPSG. However, neither mean values of the selected sleep parameters nor measures reflecting their night-to-night variability differentiated the insomniacs from the normal sleepers when such measures were derived from LPSG. In contrast, FNEs were generally absent for both subject groups when they underwent HPSG. Moreover, the insomniacs displayed significantly greater variability in several of their sleep measures during HPSG than did the normal sleepers. Overall, results suggest FNEs are a concern mainly when using LPSG, and HPSG may be more sensitive than LPSG for documenting sleep differences between normal sleepers and insomniacs. Additional studies are needed to determine if the findings reported herein are similar for young and middle-aged adults.