Occupational distribution of inflammatory bowel disease among German employees. Previous reports have shown that both Crohn's disease and ulcerative colitis affect people in white collar occupations associated with higher income and higher social class more frequently than other groups in the population. This study sought to carry these analyses one step further and investigate the distribution of inflammatory bowel disease by individual occupations. The German social security statistics for 'rehabilitation' were used to assess the occupational distribution of Crohn's disease and ulcerative colitis. From 1982 to 1988, a total of 12,014 people were granted rehabilitation as a result of inflammatory bowel disease. Low male prevalence of inflammatory bowel disease was found among bricklayers, road construction workers, unskilled workers in brick and stone, unskilled labourers, and security personnel. Low rates were found among women employed in cleaning and maintenance, and in those without occupation. In contrast, a high male prevalence was found among instrument makers, electricians, bakers, and technical assistants. Among female employees, inflammatory bowel disease was significantly associated with sales representatives, office workers, health occupations, and hairdressers. These associations were found in the complete data for 1982-8 as well as in the separate data for the two half periods 1982-5 and 1986-8. Highly significant correlations between the occupational distribution of Crohn's disease and ulcerative colitis were found among both male and female employees. It seems that occupations involving work in the open air and physical exercise are protective, while being exposed to air conditioned artificial working conditions or extended and irregular shift working confer a risk of contracting inflammatory bowel disease. 