To determine their occupational risk for hepatitis B infection, 59 Seattle paramedics were tested for hepatitis B serum markers. Evidence of antibody to hepatitis B surface antigen (anti-HBs) or antibody to hepatitis B core antigen (anti-HBc) was found in 25%, a rate five times that of a similar Seattle population. Seropositivity did not correlate with age, race, clinical history, or length of service. Of the 15 paramedics with seropositivity to hepatitis B virus, six initially had low titers of either anti-HBs or anti-HBc. Four of the six demonstrated persistent low-grade seropositivity on retesting. Paramedics are at increased risk of hepatitis B infection. The high frequency of low-titer anti-HBs suggests that frequent low-level exposure to hepatitis B virus occurs in this population; hepatitis B vaccine should be strongly considered for paramedics. © 1985, American Medical Association. All rights reserved.