OBJECTIVES: There is continued interest in identifying sources of heterogeneity in the costs of care however there is limited information available that summarizes the evidence. We characterize the reporting of heterogeneity in cost-of-illness (COI) estimates and quantify the heterogeneity in COI. METHODS: We analyzed data from a published COI review paper that reported on trends in COI methods using articles published between 2005 and 2014.  The following inclusion criteria were applied for the current study: published 2011 to 2014; stated goal of investigating patient-level heterogeneity; reported COI per patient (COIPP). We grouped articles into four categories: articles with extractable data on heterogeneity in COIPP (G1); articles with non-extractable information on heterogeneity in COIPP (G2); articles that reported COI across care settings (G3); articles that did not provide any results on heterogeneity in COIPP (G4).  Using G1, we extracted the minimum and maximum reported COI estimates across subgroups defined based on age, gender, race, disease severity, and income, among other patient-level characteristics. RESULTS: Application of the inclusion criteria resulted in 236 articles.  There were 75, 50, 98 and 13 articles for G1, G2, G3 and G4 respectively. In one study, the average patient-level COI for osteoarthritis was CAD$2,233.  The COI ranged from CAD$1,056 to CAD$3,065 and from CAD$1,985 to CAD$3,596 based on age and gender, respectively. In another study, the COIPP for childhood autism spectrum disorders was US$17,081.  The COI ranged from US$6,492 to US$25, US$9,386 to US$34,462, US$2,119 to US$18,234, and US$385 to US$10,486 across age, severity, race and income groups, respectively. CONCLUSIONS: Less than one-third of articles investigating heterogeneity reported extractable data to quantify heterogeneity in the reported COI.  Evidence regarding heterogeneity in COI can help identify differential cost burden within and across disease settings.