Dramatic improvements in sanitary engineering and, especially, operational procedures aboard cruise ships began in the mid-1970s after several large outbreaks of acute gastroenteritis. The US Centers for Disease Control and Prevention's Vessel Sanitation Program, working with the cruise industry, conducts ship inspections, provides public access to ship sanitation scores, and reports outbreak investigations. The significant increase in median ship sanitation scores over the past decade has been concomitant with a reduction in outbreak frequency to 3.7 per 1000 cruises. Most outbreaks of the past decade were linked to noroviruses (Norwalk-like viruses), enterotoxigenic Escherichia coli, or the residual "unknown" causes. Although norovirus outbreaks may begin as foodborne or waterborne disease, easy person-to-person transmission occurs through fecal- or vomitus-splattered surfaces, other items, clothing, and especially, hands. Control of person-to-person spread of illness among crew and passengers becomes the major objective. Rigorous handwashing, environmental disinfection, and other food service job-related restrictions are required to prevent multiple outbreaks on the same ship. Vigilance by public health and industry officials has prevented many thousands of illnesses and some associated deaths. Clinicians providing pretravel health advice and post-travel diagnoses and care can benefit from and contribute to epidemiologic investigations and thereby enhance the health of cruise passengers individually and collectively.