Software product lines enjoy increasingly wide adoption in the software industry. Most authors focus on the technical and process aspects and assume an organizational model consisting of a domain engineering unit and several application engineering units. In our cooperation with several software development organizations applying software product line principles, we have identified several other organizational models that are employed as well. In this article, we present a number of organizational alternatives. organized around four main models, i.e. development department, business units, domain engineering unit and hierarchical domain engineering units. For each model, its characteristics, applicability and advantages and disadvantages are discussed, as well as an example. Based on an analysis of these models, we present three factors that influence the choice of the organizational model, i.e. product-line assets, the responsibility levels and the type of organizational units.