The response to acupuncture of 18 anxious adult subjects who complained of insomnia was assessed in an open prepost clinical trial study. Five weeks of acupuncture treatment was associated with a significant (p = 0.002) nocturnal increase in endogenous melatonin secretion (as measured in urine) and significant improvements in polysomnographic measures of sleep onset latency (p = 0.003), arousal index (p = 0.001), total sleep time (p = 0.001), and sleep efficiency (p = 0.002). Significant reductions in state (p = 0.049) and trait (p = 0.004) anxiety scores were also found. These objective findings are consistent with clinical reports of acupuncture's relaxant effects. Acupuncture treatment may be of value for some categories of anxious patients with insomnia.