Nearest neighbour distances in almost all the familiar crystals have been determined from X-ray measurements which are supposed to be very accurate. These are used for the alkali halides, the chalcogenides and some Cu-, Ag- and Tl- halides to calculate the molar volume. The molecular weight, taken in grams, is divided by the molar volume, to obtain the densities of these compounds in gm /cc. These densities have been given for all the alkali halides, the chalcogenides and some Cu-, Ag- and Tl- halides. These densities, presented here, are expected to be more accurate than the values obtained by the conventional methods. In this light, use of the densities presented here should find wide acceptance for accurate work. Significant difference between the present values and those given in the standard literature exist only for a few cases. Both the sets of densities are given in the tables. However, small differences can be expected. The user will have to carefully decide which set is more appropriate for him. One may worry about the accuracy if there is a relatively large difference. Such cases are not too many.