This study examined the relationships among anxiety, nocturnal sleep, and daytime restedness over a 1-week period, using the Spielberger State-Trait Anxiety Inventory and daily sleep logs. Among both insomniacs and controls, between-subjects correlations showed a significant negative relationship between state anxiety at bedtime and restedness during the day. Neither variable was related to nocturnal sleep variables. Within-subject correlations showed similar relationships between state anxiety and restedness the following day. For insomniacs, but not for normal sleepers, bedtime state anxiety was also significantly correlated with sleep latency. The authors hypothesize that anxiety, not sleep deprivation, may be responsible for the insomniac's complaint of daytime fatigue.