Open Problems in Stringology.- 1 - String Matching.- Efficient String Matching with Don't-care Patterns.- Optimal Factor Transducers.- Relating the Average-case Cost of the Brute force and the Knuth-Morris-Pratt String Matching Algorithm.- Algorithms for Factorizing and Testing Subsemigroups.- 2 - Subword Trees.- The Myriad Virtues of Subword Trees.- Efficient and Elegant Subword Tree Construction.- 3 - Data Compression.- Textual Substitution Techniques for Data Compression.- Variations on a Theme by Ziv and Lempel.- Compression of Two-dimensional Images.- Optimal Parsing of Strings.- Novel Compression of Sparse Bit Strings.- 4 - Counting.- The Use and Usefulness of Numeration Systems.- Enumeration of Strings.- Two Counting Problems Solved via String Encodings.- Some Uses of the Mellin integral Transform in the Analysis of Algorithms.- 5 - Periods and Other Regularities.- Periodicities in Strings.- Linear Time Recognition of Square free Strings.- Discovering Repetitions in Strings.- Some Decision Results on Nonrepetitive Words.- 6 - Miscellaneous.- On the Complexity of some Word Problems Which Arise in Testing the Security of Protocols.- Code Properties and Derivatives of DOL Systems.- Words over a Partially Commutative Alphabet.- The Complexity of Two-way Pushdown Automata and Recursive Programs.- On Context Free Grammars and Random Number Generation.