Ecteinascidins are marine natural products consisting of two or three linked tetrahydroisoquinoline subunits and an active carbinolamine functional group. Their potent antiproliferative activity against a variety of tumor cells makes them attractive candidates for development as anticancer agents. The lead compound, Yondelis (trabectedin, ET-743) is the first marine anticancer agent approved in the European Union for patients with soft tissue sarcoma (STS). Positive results of a large randomized Phase III clinical trial in ovarian cancer have recently been presented. The low amounts present in its natural source, the tunicate Ecteinascidia turbinata, made it necessary to develop efficient synthetic procedures. The original total synthesis is reviewed as well as a new semisythetic process from the readily available cynosafracin B, which has solved the supply problem.