This article points out the shortage of sources for ICCs (intracluster correlation coefficients) for designing cluster randomized trials, which are important sources of information on evidence-based practices in primary care. Authors inventoried ICC estimates for shared decision-making (SDM) measures in primary care and found that ICCs were higher for process measures than for antecedent measures or outcome measures, for which, respectively, ‘‘decisional conflict’’, ‘‘reluctance to disclose uncertainty to patients’’, and ‘‘quality of the decision’’ had the highest ICCs. ICCs for provider-level clustering were higher than for other levels. This inventory of ICC estimates for SDM measures in primary care will improve the ease and accuracy of power calculations in cluster randomized trials and inspire its further expansion in SDM contexts.