Observations have been made of the 2--0 band of the Phillips system of interstellar C/sub 2/ toward the heavily obscured early-type stars VI Cygni No. 12, HD 29647, and BD +66/sup 0/1675. The first direct proof that the rotational excitation temperatures of interstellar C/sub 2/ are nonthermal was obtained. Toward VI Cygni No. 12, the rotational distribution cannot be characterized by a single, unique excitation temperature; the distribution is consistent with radiative pumping models. A very strong linear correlation was found between N(C/sub 2/) and E/sub B/-V, which suggests that the relative abundance of C/sub 2/ is insensitive to a wide variation in physical conditions.