The classic (gel-clot procedure) Limulus test (CLT) and the quantitative kinetic chromogenic LAL method (KQCL) used for the evaluation of bacterial endotoxin concentration in the indoor air of dwellings were compared. The scientific procedure included analyses of 40 air samples supplemented by the analysis of 20 sample duplicates (selected at random) which were taken during the fall season from 10 flats located in 3 towns of the Upper Silesian region (southern Poland). The particulate aerosol probes were sampled by Harvard impactor and Casella sampler. The same samples were analyzed in the Netherlands using the quantitative kinetic chromogenic LAL method, and in Poland using the classic Limulus test. Comparison of both methods revealed that the quantitative kinetic chromogenic LAL method was more precise, with better reproducibility (the coefficient of variation between analyses of the main probe and its duplicate was over two times smaller in the KQCL method than in the CLT method), fully automated in the phase of analysis and data reading, and faster and more effective than the classic Limulus test. Nevertheless, on the basis of the obtained results, the usefulness of the classic Limulus method for assessment of the degree of pollution of indoor air with bacterial endotoxin seems to be confirmed as in the majority of examined samples (21 out 40) the results obtained by both methods were of the same order of magnitude, and in the remaining 19 samples did exceed one order of magnitude. Thus, the data received by means of the classic Limulus test may be regarded as acceptable.