We analyzed the frequency of chromosomal aberrations in peripheral lymphocytes from underground miners from the Casapalca (n = 8, mean age = 45 y, range = 36 y to 55 y) and Bellavista (n = 8, mean age = 28 y, range 23 y to 34 y) high-altitude mining camps in the Peruvian Andes. This population was occupationally exposed to heavy metals such as lead and zinc as well as diesel emission particles, organic solvents and mine dust. The control groups consisted of individuals from a high altitude farming community in the Peruvian village of Tinco (n = 8, mean age = 37 y, range = 25 y to 52 y) and the sea level city of Lima (n = 14, mean age = 26 y, range = 20 y to 35 y). All individuals were male native Peruvians. A significantly higher incidence (1.88%, p < 0.05) of chromosomal aberrations (chromatid deletions and breaks, chromosome breaks and acentric fragments) were detected in lymphocytes from miners at the Casapalca camp as compared to miners from the Bellavista camp (0.5%, chromatid deletions and acentric fragments only) and the Lima sea level (0.07%, chromatid deletions only) and Tinco high altitude (no aberrations) controls. These results suggest that male native Peruvians occupationally exposed to undergfound mining activity have an increased frequency of chromosomal aberrations, which could be related to both age and exposure time. The increased chromosomal damage observed in the mining populations studied may be attributable to the complex mixture of genotoxic agents to which the miners may have been exposed. Copyright by the Brazilian Society og Genetics.