Kratom (Mitragyna speciosa) is a psychoactive plant that has been used since at least 1836 in folk medicine in Southeast Asian countries. More recently, kratom has become widely available in the West and is used for both recreational and medicinal purposes. There has, however, been little scientific research into the short- and long-term effects of kratom in humans, and much of the information available is anecdotal. To supplement the increasing scientific understanding of kratom's pharmacology and research into its effects in animals, we report the results of a qualitative analysis of first-hand descriptions of human kratom use that were submitted to, and published by, a psychoactive substance information website (Erowid.org). Themes that emerged from these experience reports indicate that kratom may be useful for analgesia, mood elevation, anxiety reduction, and may aid opioid withdrawal management. Negative response themes also emerged, indicating potential problems and unfavorable "side" effects, especially stomach upset and vomiting. Based on our analyses, we present preliminary hypotheses for future examination in controlled, quantitative studies of kratom.