This volume contains the refereed proceedings of the International Conference on Sequences and Their Applications which was held at the River View Ho tel in Singapore during December 14-17, 1998. The program of this conference was arranged by a committee consisting of Claude Carlet (University of Caen) , Agnes Chan (Northeastern University), Cunsheng Ding (National University of Singapore, co-chair), Dieter Gollmann (Microsoft Research), Tor Helleseth (Uni versity of Bergen, co-chair), Kyoki Imamura (Kyushu Institute of Technology), Andrew Klapper (University of Kentucky), Vijay Kumar (University of Southern California), Siu Lun Ma (National University of Singapore), Harald Niederreiter (A ustrian Academy of Sciences, co-chair), Dilip Sarwate (University of Illinois at Urbana-Champaign), Hans Schotten (Aachen University of Technology), Jeffrey Shallit (University of Waterloo), Neil Sloane (AT&T Shannon Lab), and Aimo Tietiivajnen (University of Turku). The local organization was in the hands of Cunsheng Ding, Kwok Van Lam (chair), Sjauntele Lau, and Sew Kiok Toh, all of the National University of Singapore. The idea for the conference grew out of the recognition that sequences in discrete structures like the ring of integers, residue class rings of the integers, and finite fields have found many important applications in modern information and communication technologies. Among these applications we mention cryp tographic schemes, ranging systems, spread spectrum communication systems, multi-terminal system identification, code-division mUltiple-access communica tion systems, global positioning systems, software testing, circuit testing, and computer simulation. There are also connections between sequences in discrete structures and error-correcting codes.