A method for calculating cooling loads was developed in ASHRAE RP-138(1) that appeared tobe more consistent and accurate than previous methods. Although comparisons of other loadcalculation procedures have been made, (2, 3) it was of interest to compare the results of RP-138method with the results of sophisticated computer routine. The NBSLD program developedby the National Bureau of Standards(4) is unique in that fewer assumptions are necessary;all load sources are applied simultaneously. The resulting cooling load and all air temperatures and all surface temperatures, including partition surfaces, reflect the interdependenceof the loads and do not require the assumptions for superposition. In general, the effect ofthis interaction would be expected to attenuate the peaks and valleys of the load profile. Thus,the NBSLD program provides an excellent reference point for comparison. It should help evaluatethe effects of the simplifying assumptions used for design day calculations. While thepeak load is of primary concern when making an equipment selection, the load profile providessome insight as to temperature drift, and possible thermal storage. The 24-hour sumof the hour-by-hour load will indicate the total energy load imposed.