The authors of this paper develop a new typology of growing and fast-growing firms, based on consistent application of the microeconomic theory of the firm, and thereby addressing some limitations of existing studies that investigate growing and fast-growing firms. A rich database available for the entire population of business entities in Slovenia enables the authors to use the proposed typology and investigate key demographic and other characteristics of firms with different types of growth in the 2007-12 period. The authors conclude that the case of Slovenia and the analysis of firm characteristics confirm the adequacy of the proposed typology.