Purpose -The purpose of this paper is to report on the use of web services to transmit requests and documents in the interlibrary loan (ILL) services of Spanish universities. Design/methodology/approach -The paper describes the problems involved in the use of email for communication between ILL services and presents a solution based on SOAP/XML technologies using standard protocols such as ISO 10160/10161, the OpenURL protocol and the NISO circulation interchange protocol (NCIP). Findings -The solution presented provides real data on ILL transactions and on the use of options for communication between services, and will be used to further develop the gathering of statistical data on the service. Practical implications -This technology provides instant confirmation of receipt of messages, eliminating the uncertainty of using email. It also synchronizes the status of requests between the requesting and supplying institutions at all times. Originality/value -Although the use of web services in ILL transactions is suggested in the NCIP, their practical application has been limited and isolated. This paper describes their implementation in Spain in practically all university libraries, the National Library and many medical libraries.