Previous studies have found that laboratory conditions influence sleep-waking behavior in older infants, children, and adults. The present study employed videotape recordings to monitor continuous 24-hr sleep-waking activity in 2- and 8-week-old infants before, during, and after 12 hr of polygraphic recordings. Sleep- and waking-state organization were affected by laboratory conditions. At both age levels, increased fussy-crying and decreased alertness occurred during the first 4 hr in the laboratory when they were video recorded only and during the first 4 hr that the leads were in place. Decreased fussy-crying and increased alertness were noted in the following periods, indicating adaptation. Latency to sleep was shorter, and drowsiness increased and active sleep decreased while the leads were in place. At 8 weeks, quiet sleep increased and active sleep decreased while the leads were in place. These data suggest that the unfamiliar laboratory conditions inherent in both observational and polygraphic studies are stressful and that time for adaptation is needed.