Neuropsychiatric behaviors are common in people with Alzheimer's disease (AD) and make both professional and lay caregiving difficult. Light therapy has been somewhat successful in ameliorating disruptive behaviors. This randomized trial tested the effects of morning or afternoon bright light exposure compared with usual indoor light on the presence, frequency, severity, and occupational disruptiveness of neuropsychiatric behaviors in nursing home residents with AD. Light was administered for 1 hr daily (Monday-Friday) for 10 weeks. The Neuropsychiatric Inventory-Nursing Home was used to assess behavior at baseline and end of the intervention. Analyses revealed statistically significant differences between groups on agitation/aggression, depression/dysphoria, aberrant motor behavior, and appetite/eating disorders. The magnitude of change was small and may not represent clinically significant findings. Agitation/aggression and nighttime behaviors commonly occurred and were highly correlated with occupational disruptiveness. Interventions that decrease the presence and/or severity of neuropsychiatric behaviors have the potential to significantly decrease caregiver burden.