A total of 115 samples of pharmaceutical raw materials (excipients) were analysed: 36 lactose, 27 talc, 19 corn starch, 18 arabic gum, 8 gelatin, 3 gelatinized starch, 3 cellulose and one tragacanth gum. 69.9% of the samples showed less than 10(2) bacteria/g (mean = 23.2 cfu/g) and 95.2% less than 10(2) fungi/g (mean = 4.92 cfu/g). Arabic and tragacanth gum were the most contaminated products by bacteria and fungi, respectively. Pregelatinized starch, cellulose and lactose were the least contaminated excipients. In none of the samples Escherichia coli or Salmonella-Shigella were detected; however, strains of Enterobacter, Serratia and Proteus were isolated from 10 samples of 5 different excipients. Only 5 samples did not comply with the microbiological standards as established by the European Pharmacopoeia and USP.