A Nd:YAG laser was operated at 1064 nm and with 6-ns pulse duration to achieve optical breakdown in gaseous hydrogen at pressures of 150 and 810 Torr. Spatially and temporally resolved laser-induced emission spectra were measured early in the plasma decay. With hydrogen-alpha line profiles, electron number density values were determined along the laser beam plasma in the range 10(19) to 10(16) cc(-1).