We have used the All Wales Injury Surveillance System (AWISS) in a population-based study of wrist and forearm fractures. We examined seasonal variation in the incidence of these injuries, and looked at resulting pressures on outpatient and inpatient trauma services. AWISS collected data from eight Accident and Emergency (A&E) departments which between them serve a total of 1.2 million people in South Wales. During a single year, we identified all 5013 people who presented with a wrist or forearm fracture. Seasonal variation in wrist/forearm fracture incidence was apparent, but showed a different pattern in different age groups. Overall incidence figures were dominated by an increase in children's fractures in spring and summer. Children under the age of 15 suffered a total of 360 wrist and forearm fractures during the three winter months; an incidence of 5.9/1000 per year that was only about half that observed during the remainder of the year (10.7/1000 per year). In contrast, older people showed a higher incidence in the winter. During the winter months people aged over 75 sustained a total of 160 wrist/forearm fractures; an incidence of 8.2/1000 per year, significantly higher than the incidence observed in other months (5.8/1000 per year). Seasonality of incidence was not apparent in other age groups. Children presenting during the spring and summer months were significantly more likely to need admission to hospital; 22.8% were admitted compared with just 10.3% of those presenting during the winter months (P<0.001, chi(2)-test). Other age groups showed no significant seasonal variation in the likelihood of hospital admission.