Although many assessment tools and methodologies for measuring knowledge management capabilities are becoming available in the practitioner world, none of them has been tested for validity. In this paper, we first present a knowledge management capability assessment (KMCA) methodology for determining the capability levels of an organization in various knowledge areas. The KMCA defines the knowledge capability areas and a five-level metric for assessing capabilities within each area. We then present the results of an empirical study conducted to validate the ability of the KMCA methodology to correctly ascertain capability levels within knowledge areas. The validation consists of two different tests: The first test, called the absolute test, validates the five-level metric within the KMCA by showing that a lower capability level is a prerequisite for achieving the next higher level. The second test, called the relative test, demonstrates the ability of the KMCA to compare relative capabilities (1) across knowledge areas within a single organization and (2) across multiple organizations for a given knowledge area. The KMCA was developed in concert with a leading manufacturing company in the semiconductor industry. The data for this study was collected from over 700 knowledge workers from multiple large organizational units within the company. The results show that the KMCA is robust, in that it is able to correctly estimate the capabilities of the knowledge areas it was designed to measure.