Adherent bacteria were released from the surfaces of four freshly extracted teeth by mild sonic oscillation, and screened for cell-surface hydrophobicity on the basis of their ability to adhere to hexadecane. Of the 103 tooth isolates examined, 82 adhered to the test hydrocarbon. Hydrophobic bacteria could similarly be isolated from the stainless steel dental matrix bands following brief incubation in the mouth of a volunteer; 30 of 52 isolates examined adhered to hexadecane. Among those strains which adhered to hexadecane, streptococci were the most frequent type isolated. Various other morphological types were also observed, including cocci, bacilli, coryneforms, and filamentous bacteria. The high overall proportion of hydrophobic bacteria found in this study (72%) suggests that cell-surface hydrophobicity may play a role in adherence of certain oral species to the tooth surface.