Eighteen poor sleepers and 18 good sleepers of mean age 52 yr, selected on the basis of their stated opinions about their sleep, were studied as pairs matched for sex, age, height and weight, on five consecutive nights and two consecutive days. Using EEG measures, the poor sleepers woke more often in the early hours of sleep and achieved half an hour less sleep. They had higher body temperatures by day and night and were more anxious. They tended to have higher urinary cortisol and adrenaline excretion. The groups did not differ in reaction time nor in excretion of urinary 3-methylhistidine. The poor sleepers over-estimated their sleep latency and both groups under-estimated their total sleep, the poor sleepers being significantly more inaccurate. It is concluded that those who complain of poor sleep have also metabolic differences from good sleepers.