Relative to the overall population of small- and medium-sized enterprises (SMEs), high-growth SMEs (HGSMEs) make a disproportionate contribution to economic growth. While research has identified factors that characterise HGSMEs, it is yet to provide a comprehensive explanation of the growth process. The purpose of the study is to identify specific growth events and examine how HGSMEs successfully transition through these periods in terms of operational (i.e. management systems and practices), structural, and strategic changes. Drawing from a descriptive profiling of Irish HGSMEs, four in-depth case studies are presented. Analysis suggests a complex relationship between structure and growth, illuminating how HGSMEs experience trigger points that create a momentum of growth, which in turn mandates a supportive infrastructure.