Purpose: Vocabulary intervention should be guided by information from outcome measures that demonstrate whether the student has grown in depth or breadth of understanding of the taught words. However, there is a paucity of tools, to measure depth of vocabulary knowledge, that are available for clinical use. Method: The challenges of vocabulary measurement are summarized. A procedure to assess semantic knowledge of specific words, both before and after treatment, is outlined: 5 yes/no questions that use the target word in different contexts (Stallman et al., 1995), and definitions, scored on a 5-point scale (Duff, 2019). These combined measures evaluate word knowledge along a wide continuum of semantic knowledge. Results: Evidence for the validity and reliability of these measures, as well as sensitivity to treatment effects, is reviewed, and implementation resources are provided for clinicians. Conclusion: This protocol can be used by clinicians to evaluate the effectiveness of vocabulary treatment by comparing a child's semantic knowledge of specific words before and after treatment.