Multichannel retailing can offer a wide range of synergies for retailers when their distribution channels accommodate consumers’ preferences and buying behaviors. Among the large number of retail types, mail-order companies are well-suited to benefit from electronic commerce. Not only can they use their infrastructure and experience with direct selling, but they also seek to use the Internet to attract new target groups in order to increase their typically small, narrow customer bases. Currently, we do not know enough about the antecedents of channel choices, especially in the mail-order sector. This article addresses this issue and draws special attention to exogenous (i.e., independent of the retailer) factors that influence online shopping behavior. These variables include perceived convenience and perceived security of online shopping in general and consumers’ attitudes toward the catalog as the existing distribution channel. One endogenous factor—attitude toward the online shop—is assumed to influence buying behavior at the online shop. In order to examine relationships between the catalog and the online shop, 2,363 consumers who were familiar with both distribution channels of a mail-order company were surveyed online. The structural equation model developed reveals that attitudes toward the printed catalog most strongly influence attitudes toward the online shop. Further, the analysis showed that antecedents of buying behavior at the online shop are moderated by gender. Shopping behaviors of men are influenced by their attitudes toward the catalog, while shopping behaviors of women are determined by their attitudes toward the online shop.