When N/sub H2/roughly-equal1-40 x 10/sup 19/ cm/sup -2/ in a given direction, or f equivalent 2N/sub H2//N/sub H/>10/sup -1.4/, the column densities of C I and H/sub 2/ are strongly correlated even though N/sub C/ /sub i/ and N/sub H/ are not. All or most of the observed C I in such directions is harbored by a single, predominantly molecular (H/sub 2/>>H I) region even when the molecular gas has as little as 5% of the total H nuclei. The interstellar carbon depletion factors derived recently by Jenkins and Shaya from C I observations correspond almost perfectly to the fraction of H nuclei in molecular hydrogen, and it appears that carbon is essentially undepleted for a sample of 15 C I--bearing regions. For a partially overlapping sample of eight directions with measured N/sub Ctsi/I, the ratio N/sub Ctsi/I/N/sub Htsi/ is generally consistent with a solar carbon abundance.