In the last decade major steps towards an algorithmic treatment of orthogonal polynomials and special functions (OP & SF) have been made, notably Zeilberger's brilliant extension of Gosper's algorithm on algorithmic definite hypergeometric summation. By implementations of these and other algorithms symbolic computation has the potential to change the daily work of everybody who uses orthogonal polynomials or special functions in research or applications. It can be expected that symbolic computation will also play an important role in on-line versions of major revisions of existing formula books in the area of OP & SF.

Many articles on the algorithmic treatment of orthogonal polynomials and special functions and on applications of such algorithms have been published in the meantime. But such articles are distributed widely in the literature. To collect these efforts Wolfram Koepf organized Session 13 on Orthogonal Polynomials at the First ISAAC Congress with the emphasis on the use of computer algebra. This congress took place at the University of Delaware, Newark, Delaware, June 3-7, 1997.

In this special issue of the Journal of Symbolic Computation we would like to collect articles about the interaction between computer algebra and orthogonal polynomials/special functions. Hopefully, the participants of Session 13 at the First ISAAC Congress will submit papers, but this special issue is open for everybody. Rather than a Proceedings of a session, the issue is meant as a state of the art account of this topic.

Contributions should discuss non-trivial usage of symbolic computation which significantly contributes to the theory of Orthogonal Polynomials and Special Functions. Examples of categories in which contributions may fall are:

• New symbolic algorithms for obtaining specific results in OP & SF. This may also be a presentation of a drastically improved implementation of an existing algorithm.
• Proofs aided by symbolic computation of significant new results in OP & SF which are yet untractable by purely human effort.
• New significant results in OP & SF which are finally provable without computer aid, but which would have been hard to find without experimentation by symbolic computation. The description of this experimentation should be illustrative for future efforts by others.
• Aspects of symbolic computation in connection with the production of on-line text books and formula dictionaries on OP & SF.

Authors are invited to submit their manuscripts to the Managing Guest Editor Wolfram Koepf preferably by e-mail in some TeX dialect or in PostScript. All submitted papers will be refereed according to the JSC usual refereeing process (see http://www.cis.udel.edu/~caviness/jsc.html for information about JSC). The journal's LaTeX style file can be obtained from ftp://ftp.udel.edu/pub/jsc (America) or ftp://ftp.risc.uni-linz.ac.at/pub/jsc (Europe).

Important dates:
Deadline for submission of full papers: Notification of acceptance/rejection: Final revised manuscripts due: Appearance of special issue:	15 January, 1998 31 May, 1998 15 September, 1998 1998/1999
Guest editor addresses:
Wolfram Koepf Konrad-Zuse-Zentrum Berlin Takustr. 7 D-14195 Berlin-Dahlem Germany koepf@zib.de	Richard A. Askey University of Wisconsin Department of Mathematics 480 Lincoln Drive Madison, WI 53706-1313, USA askey@math.wisc.edu
Tom H. Koornwinder Department of Mathematics University of Amsterdam Plantage Muidergracht 24 NL-1018 TV Amsterdam The Netherlands thk@wins.uva.nl