Dissatisfaction with the conditions of rural practice perpetuates the geographic maldistribution of physicians. This study evaluates the economic productivity of physicians who participated in an organized locum tenens (LT) service that was designed to improve practice conditions for rural physicians by making time off more feasible and less costly. The productivity of LT physicians, expressed as their average daily billing, was compared with the amount charged to rural clinics for the LT service and with the revenue billed by the clinic physicians during the same month. The clinics were charged $375/$439/day, compared with $584/day billed by the clinic physicians (p less than 0.01). The revenue billed by 85 per cent of the LTs exceeded the amount charged for their services; the revenue billed during 80 per cent of the coverage episodes also exceeded the $375/day level. When LT billing was expressed as a percentage of clinic physician billing LT productivity was found to be significantly higher in solo practices, as compared with partnership practices (97 per cent vs. 73 per cent, p less than 0.01). Assuming that a physician's overhead remains constant when he leaves, the cost of leaving a practice with LT coverage was almost invariable less than the cost of leaving without coverage. The finding justifies cautious optimism about using LTs to increase free time and improve practice conditions for rural physicians.