Ethnographic assessment of worker lifestyle and motivation was paired with measurement of health, maximum oxygen uptake, anthropometry, and cold response to predict productivity in order to determine how well behavioral ratings and biological rankings of worker capacity predict actual productivity. The subjects were Chinese laborers hauling heavy loads on a cycle by human power during a Beijing winter. Worker productivity was measured as pay for unit of work done. This paper reports the ethnographic methods and results. Worker health was assessed through a physical examination including vital signs, echocardiogram (ECG), nutrition, hemoglobin, and hematocrit. Worker motivation was assessed during 10 weeks of participant observation, extensive interview, and a visit to the worker's household. Motivation was rated using a rank-order comparison of all 50 workers from lowest to highest. Other observational ratings (household assets, demands on worker, and health of household members) were completed at the time of the home visit using five-point scales. © 1995 Wiley-Liss, Inc.