Strong H/sub 2/ lines were measured in all 11 reddened stars STAE(B-V)> 0.101 observed; the fraction f of hydrogen gas in molecular form exceeded 10/sup - 1/. In eight out of nine unreddened stars STAE(B-V) < 0.05! there was no trace of H/sub 2/ absorption, with f less than 10/sup -7 In two stars of intermediate reddening f was between 10/sup -5/ and 10/sup -6/. The relatively large column densities in higher rotational levels, up to J = 5 or 6, corresponded to excitation temperatures mostly between 150 deg and 200 deg ; the ratios of ortho- hydrogen (J = 1) to para-hydrogen (J = 0) corresponded to lower temperatures, averaging about 80 deg . Measures of two HD lines in nine stars indicated a ratio of HD to H/sub 2/ equal to about 10/sup -6/; correction for the more rapid disruption of HD molecules, in the absence of effective optical shielding by many other such molecules, indicated that one HD molecule is formed and dissociated for about every 200 H/sub 2/ molecules. (auth)