Late-instar German cockroaches from an insecticide-susceptible field strain (Fairbanks) and four pyrethroid-resistant field strains were exposed to vapors of a cyfluthrin flowable concentrate (FC) and the formulation blank (formulation without the active ingredient). Experiments with other pyrethroid formulations were done with the Fairbanks strain and an insecticide-resistant field strain (K-851) because these strains exemplified the maximum interstrain variation in experiments with the FC. In these experiments, I used a cyfluthrin wettable powder (WP) and its blank, a cyfluthrin emulsifiable concentrate (EC), and a permethrin aerosol and its blank. Vapors of the FC and its blank caused the most rapid dispersal. Dispersal induced by vapors of the WP, EC, and aerosol formulations was low and variable. In general, less of a dispersal response occurred in the resistant strains than in the susceptible strain. The strain mostly highly resistant to pyrethroids (K-851) dispersed slowly compared with the other resistant strains in experiments with the FC and its blank. When vapor-induced dispersal was relatively low (less than 50%), a trend was still evident towards less dispersal in the K-851 strain than in the Fairbanks strain. Although dispersal in experiments with the FC did not differ significantly from that in experiments with the FC formulation blank, mean percentage dispersal at the end of the experiments was higher with the formulation blanks than with the complete formulations in experiments with the WP and permethrin aerosol.