Fungal spore trap analyses currently are being marketed to the medical and environmental industries as a means of evaluating fungal bioaerosols. No studies comparing the results of these analyses have been conducted among laboratories providing these services. In the current study we compared the results from seven such laboratories with four different commercial spore trap cassettes with samples from four environmental conditions. The conditions included indoor air from a single location in a building under low, moderate and high agitation, and a sample from outside the same building. The means, ranges and standard deviations of total spore counts per cubic meter were respectively: low agitation indoor 514, 40-1933, 395; moderate agitation indoor 446, 80-1120, 290; high agitation indoor, 5154, 1510-15278, 3335; and outdoor 16012, 3700-28959, 6600. Results were similarly variable for the 27 spore categories that contribute to the total count. No consistent difference was observed in the precision of the kinds of spore traps. We concluded that spore trap analyses should be used with caution and should not be used as a sole method of assessing fungal spore populations and that standardized methods of analysis must be developed that include information about analytical precision of the sample data.