The study has carried out on 1335 workers in direct contact with petrol, has been identified without occupational melanosis in 2007, to determine the incidence of occupational melanosis in petroleum branch workers in 2008. The study for determination of working conditions, physical examination to detect skin diseases and skin darkening cases, to test biological dosimeter (Biodose) to identify cases of occupational melanosis in Vietnamese Petroleum Corporation with the following results: Incidence of occupational melanosis in workers of petroleum branch in 2008 is 6.98 percent. Incidence of occupational melanosis in workers aged over 40 years was higher in younger age groups with p 0.05. Incidence of occupational melanosis in workers over 15 years of working of higher in age groups under 15 years working with p 0.05.