Viral membrane proteins extracted from Sendai virions with the non-ionic detergents decylpolyethyleneglycol-300 and Triton X-100 were used as a model mixture of hydrophobic membrane proteins. The detergent extract contained the fusion protein (F) and the tetrameric and dimeric forms of the hemagglutinin-neuraminidase protein (HN). These proteins were purified by size-exclusion high-performance liquid chromatography (HPLC) in the presence of 0.1% sodium dodecyl sulphate, by ion-exchange and metal chelate affinity HPLC in the presence of 0.1% decylpolyethyleneglycol, and by reversed-phase HPLC without prior removal of the detergent. The tetramer of HN and F could be purified by size-exclusion HPLC after dissociation of a micellar aggregate containing tetrameric HN and multimeric F. The F and HN proteins could be purified by ion-exchange HPLC. Pure F protein could be obtained after metal chelate affinity HPLC. The F protein and the dimer and tetramer of HN could be eluted from a large-pore (100 nm) reversed-phase column, but they were eluted as broad, overlapping peaks. Only after reduction of the virion extract, the relatively small (13-15 kilodaltons) F2 protein could be obtained in pure form.