A method of transmission of application data (97) in a digital transport stream characterized in providing an application data table (110) containing information regarding the applications (97) carried in each service (91, 92) within the transport stream. The application data table (110) may conveniently be designated by a fixed PID value and a TID extension value varying in dependence on the bouquet of services chosen. The use of a single application data table to provide information across all services within a bouquet provides a number of advantages, in particular when deciding whether or not to maintain certain applications when switching between services.