Nurses are the largest professional group in health care. Nurses' smoking is not only important to their personal health, but also to the public's health. Analysis of smoking prevalences found among nurses in 21 countries in the period 1959-1988 shows that considerable numbers of both female and male nurses are smokers. More often than not there are found as many smokers among nurses as among the general population, sometimes even more. Only in Canada and Finland female nurses smoked clearly less than the population at large. Nurses' smoking prevalences decreased slowly in industrialized countries. An exemplary role is recognized by many nurses; more so by non-smoking nurses than by their smoking colleagues. Factors influencing nurses' smoking are professional socialization, duality of roles, workstress, discrepant expectancies about nurses' role and lack of social support. Theoretical explanations for nurses smoking by means of the theories of strain, of selection, of social control and of professional subculture are discussed. Future research should be internationally coordinated and aimed at comparability within a cultural and organizational context.