[en] The He(I) photoelectron spectra of the gaseous metaborates of K, Rb, and Cs have been obtained using a modified high-temperature cylindrical-mirror electron spectrometer equipped with a resistance-heated sample oven. Attempts to acquire data for LiBO₂ and NaBO₂ were unsuccessful because of the high temperature required for volatilization (on the order of 1300-1400K). The identities of the vapor-phase molecules were based on mass spectrometric and electron diffraction data. Spectral lines were assigned molecular-orbital origins through the use of MO calculations and by analogy with other compounds of similar type. (orig.)