The present invention is directed to an irinotecan acid addition salt which is formed through addition of an acid selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid, methanesulfonic acid, citric acid, maleic acid, and succinic acid to irinotecan, to a method for producing the salt, and to a pharmaceutical composition containing the salt. The addition salt requires no heating process during drug preparation and provides an aqueous drug product in which the salt is stably dissolved.
