Ciliostasis times of the water‐soluble smoke fraction of the University of Kentucky 1R1 Reference Cigarette and experimental cigarettes were compared in the hamster tracheal ring system. Dose‐responsc relations were critically examined, and the assumptions of a dilution bioassay were tested. The model in which a logarithmic transformation was used for both mean time to ciliostasis and smoke sample concentration gave the most satisfactory linear fit. At appropriate concentrations, the ciliostatic responses of the test tobacco smokes were found to be parallel to those of the 1R1, supporting the validity of the dilution bioassay assumptions. Details of experiments and analyses are presented as examples of some of the steps required to establish valid bioassay systems.