Following completion of a productivity study in Medford NJ, Warnaco, Bridgeport CT, expressed interest in a similar study in Puerto Rico, emphasizing that over the past 10 to 15 years a large segment of this country's apparel manufacturing industry had been transferred there. Since most of the older plants were not air-conditioned, but the trend toward air conditioning is growing, Warnaco was interested in knowing whether air conditioning could be shown to affect attendance and productivity of workers in Puerto Rico. Other broader concerns were (1) whether people raised in a tropical climate are as affected by daily fluctuations in temp and humidity as workers in a temperate climate; (2) whether any initial benefits of air conditioning "wear off" in time as workers became accustomed to the new conditions; or (3) whether people in air-conditioned buildings become so accustomed to a controlled environment that they grow increasingly sensitive to change and are adversely affected by even small temp variations. In 1969 the Warner Brothers Division of Warnaco was still operating an older non-air-conditioned sewing factory in Guaynabo, a small town about 12 miles from San Juan. The building had an uninsulated metal roof, unscreened windows on three sides, and a number of pedestal-mounted and other fans located throughout the working area. Conditions were said to be uncomfortably hot on many days throughout the year. This building was to be replaced in the second half of 1970 with an air-conditioned one. The new R.D. Pepler is Vice PrelJident, DunllJp and Associates, Inc, Darien CT. This paper was prepared for presentation at the ASHRAE Spring Conference, Regina, Saskatchewan, Canada, May 16-18, 1973. The research project was sponsored by T.C. 2.1 (Physiology & Human Environment) plant was to be built alongside the existing factory and the current employees transferred to the new facility as soon as it was ready. Both the factory manager and the Warner Brothers Division offered their full cooperation for a study at Guaynabo, and agreed to provide personnel facilities for collecting thermal, productivity and absence data, first in the non-air-conditioned and later in the air-conditioned plant. The Warnaco management also purchased three thermograph recorders specifically for the study.