Non-flagellate Salmonella mutants representing complementation groups H1, H2, flaAI, flaAII, flaAIII, flaB, flaC, flaD, flaE, flaF, flaK, flaL, flaM, flaN, flaP, flaQ and flaR were examined for their sensitivity to the flagellotropic bacteriophage .chi.. H1, H2, flaL and flaR mutants were sensitive to .chi. by spot tests, although they were less sensitive than a parental flagellate strain; flaAIII mutants were also sensitive, although even less so, by their ability to propagate the phage at the spotted area. In liquid medium neither adsorption nor propagation of .chi. was observed on any of these sensitive non-flagellate mutants. Electron micrographs showed the .chi. particles were attached to the superhooks of flaR mutants, but the receptor sites of other sensitive non-flagellate mutants could not be recognized.