The performance of Brazilian male and female scientists in three scientific fields was assessed through their publications in the Science Citation Index from 1997-2001. Information on their sex and their ages, positions, and fellowship status was obtained from a census on all Brazilian scientists. The results showed that women participated most in immunology, moderately in oceanography and least in astronomy. Men and women published similar numbers of papers, and they were also of similar potential impact; they were also equally likely to collaborate internationally. Nevertheless, women were less likely than men to receive fellowships to supplement their salaries, suggesting that some sexual discrimination may still be occurring in the Brazilian peer-review process.