Whereas breathalysers have been shown to provide blood alcohol concentration (BAC) measurements comparable to those obtained by gas chromatography, such evidence has not been reported in low and middle income countries where measures for preventing alcohol-related injuries are virtually non-existent. Before promoting any method of blood alcohol evaluation, as a routine procedure for monitoring the association of alcohol with different types of injuries in Kenya, we sought to assess the reliability and validity of blood alcohol results obtained by a breathalyser, using gas chromatography analysis values as the reference, in a sample of 179 trauma-affected adults presenting to casualty departments. No differences in proportions of subjects with high levels of blood alcohol (equal to or greater than 50 mg%) were detected by breath and blood test procedures (58.7 vs 60.3%). Breathalyser readings yielded high levels of sensitivity and specificity (97.2 and 100%, respectively) with optimal positive and negative predictive values (100 and 95.9%, respectively) at higher BACs (> or = 50 mg%). The study thus reaffirms that breathalyser tests are of value in detecting high blood alcohol levels and can be used to rapidly identify intoxicated subjects. The procedure is easy to perform and can be used for monitoring the association between blood alcohol level and driving in low-income developing countries.