Amiba is a Gene Expression Programming (GEP) framework for Java. GEP is, like genetic algorithms, a branch of evolutionary computing. The framework separates the process of evolution from the process of interpretation of the chromosome, allowing the use of various schemes. For example, graphs may be used as terminals and graph operations as operators in the chromosome instead of the usual double precision numbers. It implements mutation, transposition, and recombination. Options and rates are easily configured through an XML file. A mechanism to load fitness cases in bulk is also provided.