We studied oral hygiene instruction given to 109 patients in 19 Washington State dental practices to investigate the extent to which therapists targeted their efforts toward patients with high disease risk. Patients were examined prior to instruction and prophylaxes. Therapists' instructions were tape-recorded and their content analyzed: therapists' expectations were scored. There were no statistically significant associations between patients' initial plaque levels and the process/content of the oral hygiene instructions delivered. On average, therapists spent 9.4 minutes of each prophylaxis session discussing oral hygiene. Therapists were judged more genuine with those patients for whom they had higher expectations of compliance, i.e., those with less plaque and low disease risk. We conclude that dental practitioners were not employing effective risk assessment strategies in selection of patients most in need of intensive instructional efforts.