Volume 8 of Trends in Functional Programming (TFP) presents some of the latest research results in the implementation of functional programming languages and the practice of functional programming. It contains the peer-reviewed selection of the best articles presented at TFP 2007, the Eighth Symposium on Trends in Functional Programming, which was held in New York City on April 2–4, 2007. This was the first time the TFP symposium was held in the USA and it brought together a truly international milieu of researchers, students, and industry professionals that proudly made this edition of the symposium the largest in TFP history. The topics covered in this volume include, among others, gradual typing, semantics, memory utilization and performance, hybrid types and contracts, test generation, efficient compilation of web applications, library development, and program correctness. The authors include well known veterans in the field of functional languages as well as newcomers that are quickly becoming well-established. This volume is an essential part of any modern programming languages library. The new results described in this volume are applicable to a wide array of programming languages and readers will benefit from exposure to the latest trends in solving modern Computer Science problems. The success of TFP symposia represents the growing importance of functional programming and the growing importance of the TFP policy to encourage new and veteran speakers to present their novel work at a friendly forum without first having to go through a strenuous review process. This policy has lead to a series of symposia with a rich diversity of talks from which a selection of publication-ripe articles are chosen for inclusion in a post-symposium peer-reviewed volume as the present one.