The survival effect in mortality studies was investigated by examining the mobility of underground coal miners who did and did not use diesel engines. Whether the presence of this additional potentially harmful respiratory exposure (diesel emissions) accelerated the rate of mobility was examined. Whether miners with respiratory impairment or symptoms of respiratory illness left jobs with a potentially harmful respiratory effect in disproportionate numbers was also examined. Mines using diesel engines were matched with a control mine near the diesel operation. Miners under 50 years of age were given chest radiographs, lung function tests, and completed questionnaires on respiratory symptoms and demographic data in 1977. In 1982, updated work rosters were examined. The overall mobility, expressed as percentage leaving in 5 years was identical for both mine types, 26 percent. In both types of mines, women had a significantly higher mobility rate than men (62 percent versus 25 percent); whites had a significantly higher mobility rate than non whites (27 percent versus 15 percent); and never married and not currently married miners had higher mobility rates (32 and 40 percent) compared with 25 percent for married miners. Mobility was positively and significantly correlated with education and negatively correlated with mining experience. Miners with severe airways obstruction, moderate pulmonary restriction, or persistent productive cough, phlegm, and shortness of breath were no more likely to leave employment than healthier coworkers. Respiratory symptoms were not significantly related to mobility within mine type nor were there significant differences between mine types within respiratory symptom categories. The authors conclude that miner job mobility is based on many social factors but no support is shown for the survival component of the healthy worker effect in this group of diesel and non diesel coal miners.