The effect of a motorcycle lights-on law in North Carolina was examined by analyzing accident data for a six year period from 1972 through 1976. The law was implemented on September 1, 1973 when motorcycle activity was declining after reaching a peak during the summer months. The proportions of motorcycle crashes that were daylight multivehicle were compared with the similar proportions for all crashes. It was found that a significant decrease in these crashes occurred for motorcycles following the implementation of the law. A similar decrease was not observed for total crashes. It was concluded that the motorcycle lights-on law had the desired impact on daylight multivehicle crashes.