The 1st International Workshop on Conditional Term Rewriting Systems took place in Orsay (University of Paris-Sud) in July 1987, and brought together most of the researchers involved in the field. Conditional rewriting has actually known important breakthroughs during the last two years; it was the purpose of the workshop to put the results together, to present new, original contributions to the domain, and to discuss still unsolved issues. These contributions are reported in the proceedings. The main questions that have been addressed are the different semantics for conditional rewriting and their classification, possible extensions to the basic formalism, and the relationship between conditional rewriting and logic programming. Also, more practical issues such as applications and implementations of conditional term rewriting systems have been addressed. Descriptions of seven actual systems allowing conditional rewriting are included