The prevalence and distribution patterns of trauma in samples of human skeletal remains can reflect the risks to which the community was exposed in daily activities or as a result of interpersonal violence. This paper describes the patterns of non-vertebral fractures in skeletal samples from four prehistoric Thai sites in terms of long bone fracture rates and individual prevalence rates. The sites range in date from c. 2000 BC (Neolithic) to 400 BC (late Bronze Age), and in environment from coastal estuarine to seasonally dry upland plains. These differences in the natural and cultural environment provided a basis for comparison among the samples representing nearly 300 adult individuals. The types of fractures ranged from simple to severe, but most had healed successfully with few limiting complications. The small bones of the hands and feet as well as clavicle and forearm bones were most frequently fractured among all samples. Overall there was an increase in the major long bone fracture rates from the Neolithic (0.3%) to the Bronze Age (3.0%) that may reflect a change in subsistence activities such as land clearance for the intensification of rice agriculture. The prevalence of ulnar fractures is particularly high in the Bronze Age, and the analysis of their possible cause, combined with evidence for craniofacial fractures, is suggestive of the presence of interpersonal violence in a small number of individuals. Copyright © 2006 John Wiley & Sons, Ltd.