This Recommendation defines how Abstract Syntax Notation One (ASN.1) modules are usable in combination with Specification and Description Language 2010 (SDL-2010). The intention is that the structure and the behaviour of systems are described with SDL-2010, while parameters of exchanged messages are described with ASN.1. This Recommendation defines a mapping of ASN.1 constructs to already existing SDL-2010 constructs and contains only a small extension to Recommendations ITU-T Z.101, ITU-T Z.102, ITU-T Z.103 and ITU-T Z.104 to allow ASN.1 modules to be used.