Purpose: To analyse the microbial flora in specific sites in 20 dentate (>= 16 teeth) subjects with hyposalivation due to medicines or of unknown origin and in 20 controls matched according to age, sex and number of teeth. Materials and Methods: The microbial samples were analysed for the following micro-organisms: mutans streptococci, Lactobacillus spp. and Actinomyces spp., associated with the development of caries, Fusobacterium nucleatum and Prevotella intermedia/Prevotella nigrescens, associated with plaque accumulation and gingivitis, Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis, frequently found in elevated numbers in periodontitis sites and Candida albicans, Staphylococcus aureus, enterics and enterococci, associated with mucosal infections. The total microbial count was also registered, together with the total number of streptococci, associated with good oral health. Results: In the hyposalivation group, the mean age was 54 ± 8 years and the mean number of teeth 25 ± 3. The unstimulated secretion rate was 0.04 ± 0.04 mL/min and the stimulated secretion rate 0.98 ± 0.51 mL/min. Compared with the controls, the hyposalivation group tended to harbour a lower number and proportion of F. nucleatum on the tongue, and an increased number of enterococci in the vestibular region. In the supragingival plaque, the numbers of Strepococcus mutans and Lactobacillus spp. were significantly increased and the number of C. albicans tended to be increased. Conclusion: The results indicate that subjects with hyposalivation due to medicines or of unknown origin have a supragingival plaque associated with the development of caries. Parole chiave: hyposalivation, microflora, mutans streptococci, Lactobacillus spp., Fusobacterium nucleatum, Prevotella intermedia/Prevotella nigrescens, Candida albicans, Staphylococcus aureus, enterics, enterococci