This Special Part of the ANZIAM Journal contains the refereed papers from the twelfth Biennial Computational Techniques and Applications Conference (CTAC2004) held at The University of Melbourne in September 2004. The CTAC series of conferences is held under the auspices of the Computational Mathematics Group of the Australian and New Zealand Industrial and Applied Mathematics (ANZIAM) division of the Australian Mathematics Society. They provide a forum for scientists, engineers, and mathematicians interested in the development of computational techniques and their application to problems of practical importance. Previous conferences in the CTAC series were held at University of Sydney (1983), University of Melbourne (1985), University of S...