We aimed to provide a better estimation of health-related motorcycle fatalities by comparing the backgrounds, mechanisms of injuries, and injury severity of victims who died of collision versus those who died of disease. We retrospectively analyzed autopsy records of 29 motorcyclists (mean age, 61.0 ± 21.0 years), none of whom had been driving under the influence of alcohol. Altogether, 22 (75.9%) had died of trauma, and 7 had died of disease. The disease-death victims were significantly older and had a significantly higher prevalence of a medical history compared with those with trauma-related death (100% vs 45.5%, P = 0.01), especially of lifestyle diseases (100% vs 13.6%, P < 0.001) and heart or cerebrovascular disease (57.1% vs 13.6%, P = 0.02). All of the victims who were affected by disease and 50% of trauma-death victims had fallen on the road without a vehicle collision (P = 0.02). Mean Injury Severity Score of the trauma-death group was significantly higher than that of the disease-death group (48.1 vs 9.1, P < 0.001). A forensic autopsy should be performed for all motorcyclist fatalities to diagnose a disease-related death during motorcycle riding. To reduce the incidence of these accidents, motorcyclists should maintain a good physical status.