Lithium tetra-arsinoaluminate, LiAl(AsH2)4, reacts with halogeno-silanes and -germanes to produce the corresponding, primary silyl- and germyl-arsines. Silyl-, germyl-, disilanyl-, and trimethylsilyl-arsine have been obtained in higher yields than from previous methods. Methylsilyl-, methylgermyl-, and trimethylgermyl-arsine have been prepared for the first time and their i.r. and 1H n.m.r. spectra are reported. The two new germylarsines have also been prepared by exchange reactions between silylarsine and the halogenogermanes. Some typical reactions of primary silyl- and germyl-arsines are described.