Chemical control, by dipping or spraying infested cattle with ixodicidal compounds, is the only practicable method of dealing with the cattle tick problem in the short term.Widespread exposure to ixodicidal compounds, often at subeffective concentrations, has resulted in the selection of resistant strains from tick populations.A situation has now been reached where cattle ticks in widely separated parts of the world have shown a capacity to develop resistance to most of the currently available chemical classes of ixodicide. There is a very real probability that these resistant strains will eventually replace susceptible tick populations, particularly in those areas where the cattle tick problem is already most acute. Research and development of new chemical groups of compounds with high ixodicidal activity and low mammalian toxicity is a matter of some urgency.In this review, the biological background of the tick problem is outlined. A brief history of the development of tick resistance to arsenic, organochlorine, organophosphorus and carbamate compounds is given. Reference is made to the underlying biochemical mechanisms involved. Some of the human factors affecting the development of tick resistance are examined and future prospects are assessed.