The Raman spectrum of pure liquid di-t-butylberyllium and the infrared spectrum of the compound in the liquid and vapour phases have been recorded, together with the infrared spectrum of the vapour of [2H9]di-t-butylberyllium. Analysis of these results, in conjunction with related measurements for di-t-butylzinc and existing data for other t-butyl derivatives, is essentially consistent with a monomeric beryllium compound with a linear C–Be–C skeleton.