It is well known that requirements specification is the critical success factor for developing information systems. However, the quantitative index to evaluate the requirements specification capability of the system development organizations has not been known. This paper proposes a requirements specification capability index to evaluate information system development organizations. The requirements specification capability index is defined based on the 6 dimensions, that are requirements vision development, requirements communication, requirements product design, requirements process design, requirements investment, and requirements human resource development. The proposed capability index has also been applied to several Japanese software development organizations. The result shows that the capability index can effectively be applied to visualize the requirements specification activities of the organizations from the 6 dimensions.