We develop the beginnings of a grounded theory of entrepreneurship based on the idea that entrepreneurship, in terms of a changing opportunity structure–-consisting of opportunity detection, opportunity facilitation and motivation to pursue opportunity–-can be viewed through a paradoxical perspective that considers the interplay of organizational and individual capabilities as virtuous and vicious spirals across time. The virtuous spiral led toward successful change because of supportive organizational and individual capabilities across time. The vicious spiral led away from successful change because of countervailing organizational and individual capabilities. Paradoxically, however, we found that entrepreneurship developed in both types of spirals. We discuss these points based on two case studies of Finnish banks and bank managers within the fundamentally changing opportunity structure of the banking business in the late 1980s.