This study is about developing a theoretical and methodological framework for assessing the impact of microfinance services on the growth of micro and small enterprises in developing countries. Different theories are discussed in the study in order to explain how environmental factors, motivational factors and critical or strategic resources like credit and training can create possibilities for the micro and small enterprises growth. Through these theories and findings of previous studies, the conceptual framework was developed. The framework shows how the interventions of microfinance programmes can be assessed to determine the changes brought by the programmes. Although, additional credit and training received observed to spawn the growth of micro and small enterprises by previous studies, empirical testing is important to assess whether other factors contribute to the growth of supported enterprises. This can be achieved because the framework developed can be used to assess whether there is a difference in growth indicators of an enterprise before and after microfinance intervention and among those experienced an intervention against the enterprises experienced no intervention.