The DNA sequences encoding the amino-terminal signal peptide or the carboxy-terminal hydrophobic anchor have been deleted from a cloned gene coding for the haemagglutinin (HA) of influenza virus. The wild-type gene has previously been shown to be expressed with high efficiency from simian virus 40 (SV40)-HA recombinant vectors into a fully glycosylated protein that is displayed on the infected cell's surface in an antigenically and biologically active form. The anchor-minus HA also is glycosylated but is secreted efficiently into the medium. By contrast, the signal-minus HA is produced only at low levels, is not glycosylated and is located intracellularly.