There is a growing concern about environmental impacts resulting from construction activities. To help minimize the environmental impacts from construction, Environmental Management Systems (EMSs) have been advocated and in some cases, implemented. Within the construction industry, Environmental Performance Assessment (EPA) forms one of the most important tools in monitoring and evaluating environmental performance. However, the relations between Environmental Operational Indicators (EOIs) (inputs) used in EPA and Environmental Performance Indicators (EPIs) (outputs) have not been tested and correlated, casting doubt on the reliability of these inputs. This paper attempts to develop a series of input (EOI) and output (EPI) indicators for EPA and measure their relations based on the perceptions of project managers. The results show that EOIs defined correlate strongly with EPIs. Therefore, EPA can help to identify areas for continuous improvement, and also provide an early indication of the environmental performance for an organization.