Hello yes, i did it! today i spend time to optimize my own Binary library and got the (de)serialization speed about 50 mb/s with my 1 ghz cpu. it is a peek speed for unboxed arrays, in real life GC times and other overhead expenses will need much more time than (de)serialization itself. but at least noone can now say that serialization is a bottleneck of Haskell program :) i uploaded current version to http://freearc.narod.ru/Binary.tar.gz Main.hs in package is a testing program which builds, puts to memory buffer and then gets back a 40mb array and prints runtime of each operation Joel, if you are interested in switchinh to my library - write me. i have ideas about supporting your 150 records using your own DDL. smth like this: data Command = Cmd1 field1 Word32 333 field2 Word16 0 | Cmd2 field3 String "" field4 [SubRecord] [] you will describe all your records just one time and then these definitions will be compiled for the language/library you are using -- Best regards, Bulat mailto:bulatz@HotPOP.com