Data from the 1975, 1982, and 1990 French censuses and the Permanent Demographic Sample were used to analyze the accommodations made in different sectors of industry to age-related difficulties in job performance. The aging of the population, the greater economic activity of middle-aged women, and changes in the conditions and organization of work may have reduced the feasibility of modes of human resources administration based on reassignment of older workers or those with seniority to less physically demanding jobs. The number of workers in the principal industrial sectors declined considerably between 1975 and 1990. The proportion of young workers declined in almost all industrial sectors except food industries. Reductions through retirement had the effect of concentrating workers in the intermediate age cohorts. Middle-aged workers are increasingly confronted by working conditions that previously affected primarily younger workers. Data from the Permanent Demographic Sample, although not directly comparable to the census data, indicate that worker turnover within sectors was considerable throughout the period. Over 40% of workers in a given sector in 1975 were no longer working in that sector in 1982, and half to two-thirds of workers in a sector in 1982 were no longer there in 1990. The sectors with the highest rates of departure were generally those with the largest declines in number of workers. It may become necessary in the future to adjust to an older work force through workplace modifications to compensate for their physical deficiencies rather than by adjusting the age structure.