This study aimed to determine the prevalence rates of helmet use, and of correct helmet use (chinstrap firmly fastened) among motorcycle riders and their passengers in Zhongshan, Guangdong Province, China. A cross-sectional survey involving direct observation of motorcycle riders was conducted at 20 randomly selected intersections. A total of 13,410 motorcycles were observed during a 10-day period in February 2009. The overall prevalence of helmet use was 72.6% (95% CI: 71.8-73.3%) among drivers and 34.1% (95% CI: 32.7-35.5%) among pillion passengers. The prevalence of correct use was 43.2% (95% CI: 42.4-44.0%) and 20.9% (95% CI: 19.8-22.1%) for drivers and passengers respectively. The helmet wearing rate on city streets was almost 95%, however city riders were more likely than rural riders to wear non-motorcycle helmets while riding. In multivariate analyses, factors associated with increased helmet use included riding on city streets, male gender, being a driver, carrying less passengers and riding a registered motorcycle. The results indicated enforcement and education activities need to be strengthened with respect to both helmet use and helmet quality, especially in rural areas, in order to improve wearing rates.