The LaNi system has been reinvestigated in the range 50–100 at. % Ni. The following compounds were observed: LaNi, LaNi 1.4, LaNi 2, LaNi 3, La 2Ni 7 and LaNi 5. For these compounds the lattice constants have been determined. The phase LaNi 5 has a relatively large homogeneity region at elevated temperatures. For the compounds LaNi x within this region the equilibrium hydrogen pressure, p, of the 40 °C isotherms was found to change from 2.75 atm for LaNi 4.9 to about 9.2 atm for LaNi 5.4 according to In p = Cx + q with C = 2.4, q = − 10.75.