Inefficiency is common in many of the world’s water utilities, especially in developing countries. The problem derives from a range of different causes relating primarily to technical, organizational, and commercial (TOC) factors. Evidence from a World Bank study conducted in 2020 shows that most Zambian commercial utilities (CUs) face inefficiency challenges in their operations. This report details the state of Water Supply and Sanitation (WSS) efficiency in Zambia, focusing on three provinces: Central, Southern, and Luapula. The report is organized into six chapters. Chapter 1 outlines the background and lays out the report's objectives with a brief indication of the approach used for the assessment. Chapter 2 is a review of the state of WSS efficiency in Zambia. In addition to stating the efficiency bottlenecks in WSS delivery, the section highlights the flaws and misconceptions of performance indicators (PIs) that could hinder CUs' efforts to identify the priority areas requiring investment. Chapter 3 describes the method used to assess the technical, operational and commercial efficiency of the three pilot CUs. The section emphasizes i-TOC as an assessment tool that overcomes the flaws of traditional PIs and their application in setting targets. Chapter 4 presents the main findings from the assessment, while chapter 5 summarizes the key findings, and section 6 concludes with interim recommendations, which will be further developed.