Background In Mexico, as in other low and middle income countries, the use of motorcycles has become a popular and increasing mean of transportation. During 2009, 1.2 million motorcycles were registered. This represents 1114 motorcycles per 100 000 inhabitants, figure that has tripled in the last decade.

Objective To estimate the prevalence of helmet use and the prevalence and factors associated to non-standard helmet use (NSHU) among motorcyclists of Cuernavaca.

Methods A cross-sectional study that included observations on public thoroughfare and a survey in a sample of motorcyclists stopping at petrol stations was performed by researchers of the National Institute of Public Health. Data were collected on a daily basis, during daylight hours in February–March 2009 and March 2010.

Results 1286 motorcyclists were observed. Prevalence of helmet use was 78%. Helmet use was higher in drivers (84%) than passengers (37%) and amongst males (81%) compared to females (42%). From the 493 motorcyclists interviewed, prevalence of NSHU was 64.8%. Compared to those with bachelor or higher studies, those with secondary school (OR=1.80, 95% CI 1.01 to 3.19) and those with elementary or less school (OR=3.48, 95% CI 1.14 to 10.50) showed more NSHU. Travelling for leisure activity or riding for pleasure (OR=0.25, 95% CI 0.12 to 0.51), travelling in a <500 cc motorcycle (OR=4.14, 95% CI 2.12 to 8.06), and not owning the motorcycle (OR=0.53, 95% CI 0.34 to 0.82) also showed association.

Significance Current legislation does not require helmets to be ‘standard’. Given the lack of information about actual security and protection provided by non-standard helmets, the high prevalence of non-standard helmet use found raises the need to change Mexicans laws.