As a result of the rising problems of poverty and unemployment in African countries, there is now growing interest in the development of the small and medium enterprise sector. The interest given to small and medium enterprises rests on the belief that such firm's serve as a medium to stimulate economic growth and development in the African region. This is not only in terms of their contribution to the overall development of a nation, but also due to their ability to contribute to employment creation and development of new niche markets. Despite the significant role played by small and medium enterprises in the economic development of a nation, their performance in Africa has been disappointing. A better understanding is therefore needed of the factors which influence the performance of the small and medium enterprise sector, thus achieving sustainable economic development. Accordingly, this study aims to explore the factors that influence small and medium enterprise growth in Nigeria. In particular, the study focuses on three broad growth influences: the characteristics of the owner/managers, the nature of the firm and the external environmental influences. A mixed method approach involving the use of self administered questionnaire and semi-structured interview was adopted to achieve the aims of the study. The target sample consisted of the owners and managers of small and medium enterprises in five cosmopolitan cities in Nigeria. In total, 523 owner/managers took part in this study. In addition, the research utilised simple statistical techniques to analyse the data. The findings indicate that firm growth is influenced by a combination of owner/manager, firm characteristics and external factors. In particular, the results of the analysis in relation to the characteristics of the owner/manager revealed that age, in relation to middle-age and older owner/managers and motivation, in relation to employment creation influence firm growth. Furthermore, the result on the characteristics of the firm indicates that firm size was the most significant influence on firm growth. In relation to external factors, the result show that constant electricity interruption, corruption of government officials, poor quality roads, problems with collateral for banks and technological factors were significant influences on firm growth. From the research that has been undertaken, the key research questions were answered, conclusions and recommendations were then made. It is anticipated that the study can provide SME policy makers and advisory services with guidelines to improve the growth of the SME sector in Nigeria. In addition, it is hoped that the study will assist SME owner/managers recognise those factors which may influence their firm growth and take appropriate measures to address them.