The strength and regulatory characteristics of the heat-inducible HSA1, HSA2 and TPS1 promoters were compared with those of the well-established, carbon source-regulated FMD promoter in a Hansenula polymorpha-based host system in vivo. In addition, the Saccharomyces cerevisiae-derived ADH1 promoter was analysed. While ADH1 promoter showed to be of poor activity in the foreign host, the strength of the heat shock TPS1 promoter was found to exceed that of the FMD promoter, which at present is considered to be the strongest promoter for driving heterologous gene expression in H. polymorpha.