The potential offered by biomass and solid wastes for solving some of the world’s energy problems is widely recognised. The energy in biomass may be realised either by direct use as in combustion, or by upgrading into a more valuable and usable fuel such as fuel gas, fuel oil, transport fuel or higher value products for the chemical industry. This paper is concerned with conversion and upgrading by pyrolysis and briefly describes the technologies of fast pyrolysis with particular reference to the use of catalysts in chemicals production and the use of catalytic processes in upgrading the primary pyrolysis products to higher quality and higher value fuels and chemicals. There are natural catalysts in biomass which substantially influence the production of high yielding chemicals. Removal or reinforcement of these catalysts has a dramatic effect on product yield and composition. The pyrolysis vapours can be catalytically cracked over zeolites to give aromatics and other hydrocarbon products which can be further converted into gasoline and diesel and the condensed liquid can be hydrotreated to a naphtha like product also for upgrading into transport fuels. There is, however, considerable uncertainty over the ability of the upgrading technology to be scaled up to commercial feasibility most notably in terms of catalyst performance and life. Considerably more research and development is needed to develop and prove suitable catalyst systems. There is also considerable uncertainty over the cost of upgrading in terms of capital costs. operating costs and performance and some preliminary estimates are included.