The conductivity of single crystals of 9-methyladenine(6-amino-9-methyl-purine) has been determined using proton-injecting solution electrodes. The conductivities parallel and perpendicular to the (100) plane are 2.5 ± 1.9 × 10 -13/ohm-cm and 7.0 ± 2.9 × 10 -15/ohm-cm, respectively, at 295°K. The H-bonded pathways lie in the (100) planes. The conductivity is ohmic over the range of applied fields. The temperature dependence of the conductivity was determined parallel and perpendicular to the (100) planes.