Benzidine dihydrochloride crystallizes in the triclinic system. The space group is $P_1$. The unit cell dimensions are; a = 4.38${pm}$0.01, b = 5.76${pm}$0.01, c = 12.82${pm}$0.02${AA}$, $alpha$ = 101.5${pm}$0.2, $eta$ = 99.5${pm}$0.2, $gamma$ = 99.5${pm}$0.2$^{circ}$; with one molecule per unit cell. The crystal structure has been solved by two dimensional Patterson and by trial and error methods, and refined by means of two dimensional differential synthesis. The bond distances are C-C(*) = 1.40${pm}$0.02, C-C = 1.52${pm}$0.02, C-N = 1.51${pm}$0.03 and N-H${cdot}{cdot}{cdot}$Cl = 3.21${pm}$0.03${AA}$. The structure consists of hydrogen bonded molecular layers, extending to the (100) plane, and the hydrogen bonding scheme is similar to that of p-phenylenediamine dihydrochloride. The adhesion between hydrogen bonded molecular layers is due to van der Waals forces