To obtain comprehensive information about the knowledge, attitudes, and practices of Minnesota dental hygienists and registered dental assistants, a questionnaire was mailed to random samples of both groups in the fall of 1988. Most assistants and hygienists claimed to always wear gloves, but substantially fewer indicated always wearing a mask. Use of eye protection showed even lower compliance, with less than half of either group routinely using protective eyewear or a face shield. Assistants and hygienists reported incurring numerous needlesticks and instrument injuries. A contributing factor may be that many staff were still recapping needles with an unprotected hand. Most people who had not been vaccinated against hepatitis B said that they would be immunized if their employer or health insurance paid for it. Less than one-half of either group felt knowledgeable about infection control. Only one-third of assistants and less than one-half of hygienists claimed to be familiar with the Centers for Disease Control's "Recommended Infection Control Practices for Dentistry." This is consistent with assistants' and hygienists' reported infection control related behaviors. Other than gloving, many recommended infection control measures--masking, wearing protective eyewear and uniforms, hepatitis B immunization, and proper handling of sharps--were not employed by a substantial number of respondents. Many respondents indicated insufficient knowledge to safely and effectively care for patients with hepatitis B, hepatitis B carriers, or individuals infected with the human immunodeficiency virus (HIV). This is reflected in the relatively small percentages of respondents who indicated willingness to treat these patients.(ABSTRACT TRUNCATED AT 250 WORDS)