The trisilylamines (Me₃Si)_nN(SiMe₂H)_3–n(n= 0, 1, 2) and (Me₃Si)₂N·Si(Me₂)Ph are reported. The SiH function in the former compounds is very inert in addition reactions with alkenes and in hydrolysis but can be halogenated normally. The hydrolytic stability of the compounds has been compared with that of other types of SiN compound and shown to be high. In particular, (Me₃Si)₂NBu^t is hydrolysed much more rapidly than (Me₃Si)₃N. This result is discussed.