Hairdressers are exposed to high concentrations of formaldehyde during the hair straightening procedure, Abstract The fact that hairdressers are exposed to toxic substances through the handling of creams and smoothing products prompted this study whose aim was to quantify the occupational exposure of hairdressers to formaldehyde by comparing the results of exposure for different types of beauty salon. The study population consisted of 23 beauty salons located in the city of Bauru, São Paulo state, Brazil. The samples were collected by inhaled air tests during the most critical 15-min period of the hair straightening procedure and during the 8-h work shift. The concentrations of formaldehyde contained in the formulations of these products were also evaluated and compared with exposure levels. The results were evaluated according to the exposure limits prescribed in Brazilian (NR15) and North American (US OSHA and US NIOSH) standards. The analysis of the smoothing products showed concentrations of formaldehyde of between 3 and 11% in their compositions, i.e., up to 54 times above the 0.2% limit allowed by the National Agency of Sanitary Surveillance (ANVISA). The present study showed that hairdressers are chronically exposed to high concentrations of formaldehyde in the workplace and these exposures are mainly associated with the work process, where many variables of this process influence the intensity of exposure.