This volume contains the papers presented at the 4th Fuji International S- posium on Functional and Logic Programming (FLOPS 99) held in Tsukuba, Japan, November 11 13, 1999, and hosted by the Electrotechnical Laboratory (ETL). FLOPS is a forum for presenting and discussing all issues concerning functional programming, logic programming, and their integration. The sym- sium takes place about every 1.5 years in Japan. Previous FLOPS meetings were held in Fuji Susuno (1995), Shonan Village (1996), and Kyoto (1998). 1 There were 51 submissions from Austria ( ), Belgium (2), Brazil(3), China 3 3...