Macroreticular poly（styrene-divinylbenzene） membranes of 0.2 mm thick have been synthesized by the bulk polymerization. The effects of the contents of the crosslinking agent and the diluent on the surface area and the swelling ability of the membranes were investigated. The swelling ability and the surface area increased with the amount of diluent. With the increase in the amount of crosslinking agent, the surface area increased while the swelling ability decreased. The membranes were sulfonated with concentrated sulfuric acid in the presence of nitrobenzene and the ion-exchange capacities of the membranes were measured by titration. The ion-exchange capacities increased with the increase in the diluent content but decreased with the increase in the crosslinking agent.