The invention relates to a method for the cost-effective and environmentally friendly production of alkyl indium sesquichloride in high yield and with high selectivity and purity. The alkyl indium sesquichloride produced according to the invention is particularly suitable, also as a result of the high purity and yield, for the production, on demand, of indium-containing precursors in high yield and with high selectivity and purity. As a result of the high purity, the indium-containing precursors that can be produced are particularly suitable for metal organic chemical vapor deposition (MOCVD) or metal organic vapor phase epitaxy (MOVPE). The novel method according to the invention is characterized by the improved execution of the method, in particular a rapid process control. Owing to targeted and extensive use of raw materials that are cost-effective and have a low environmental impact, the method is also suitable for use on an industrial scale.