The small vertebrate, zebrafish, has generated a big wave in current biomedical research. In the early experiments of carcinogen treatment, it has been found that the induced tumors in the zebrafish share many similar features with those of humans. With the recent development in transgenic technology, we are able to control the expression of a specific oncogene in targeted organs for generation of different tissue tumor models in zebrafish. In particular, the fusion of an oncogene and a color reporter, such as the green fluorescent protein, allows us to conveniently monitor transgenic tumors for their initiation, progression, metastasis and transplantation in the transparent zebrafish embryos, as demonstrated in this article with our newly established liver cancer models. What does the future hold in this rapidly growing model organism? Other than understanding the molecular mechanisms of carcinogenesis, one obvious area will be the potential of these models for rapid and high-throughput screening for anticancer drugs.