Most large, successful companies began as insurgents—fast, agile and adaptable. They focused on customers. They hated complexity. But too many companies accept a troubling trade-off. They achieve scale, but lose their Founder’s Mentality—the very core strengths and values that helped them succeed and grow. Our research shows that of the one in nine companies that achieve a decade or more of sustained, profitable growth, the majority are those that have preserved—or restored—their Founder’s Mentality.