Background: : Kratom is a botanical product used as an opium substitute with abuse potential. Methods: : Assessment of suspected cases of kratom-induced liver injury in a prospective US cohort. Results: : Eleven cases of liver injury attributed to kratom were identified with a recent increase. The majority were male with median age 40 years. All were symptomatic and developed jaundice with a median latency of 14 days. The liver injury pattern was variable, most required hospitalization and all eventually recovered. Biochemical analysis revealed active kratom ingredients. Conclusion: : Kratom can cause severe liver injury with jaundice.