Objectives.To identify healthcare worker (HCW) and work-site characteristics associated with HCWs' reported use of recommended respiratory-infection control practices in primary and emergency care settings.Design.A cross-sectional study using a self-administered questionnaire for HCWs during the summer and fall of 2005.Setting.Primary and emergency care clinics at 5 medical centers in King County, Seattle, Washington.Results.Nurse professionals who reported receiving training (odds ratio [OR], 2.5 [confidence interval {CI}, 1.1–5.9]; P = .029), instructional feedback from supervisors (OR, 3.0 [CI, 1.5–5.9]; P = .002), and management support for implementing safe work practices had a higher odds of also reporting adherence to recommended respiratory precautions, compared with nurses who did not. Training was the only important determinant for adherence to respiratory precaution measures among medical practitioners (OR, 5.5 [CI, 1.2–25.8]; P = .031). The reported rate of adherence to hand hygiene practices was higher among nurse professionals who were male (OR, 2.2 [CI, 1.0–4.9]; P = .045), had infants, small children, or older adults living at home (OR, 2.2 [CI, 1.2–3.9]; P = .007), reported cleanliness and orderliness of the establishment where they worked (OR, 2.0 [CI, 1.1–3.5]; P = .019), had received respiratory-infection control training (OR, 3.2 [CI, 1.8–6.0]; P<.001), and reported fears about catching a dangerous respiratory infection at work (OR, 2.3 [CI, 1.2–4.5]; P= .011).Conclusion.A number of HCW and work-site characteristics associated with HCWs' use of recommended respiratory-infection control measures have been identified. These potentially influential characteristics should be considered as targets or guides for further investigation, which should include the evaluation of intervention strategies.