Factors affecting the performance of acaricides in the control of ticks are reviewed. A survey of studies on the deposition of acaricides on the hair of dipped or sprayed cattle shows that acaricides in suspension form metastable systems. Their physical instability is initiated or accelerated by additives, ageing, fouling and replenishment and is manifested as marked changes in the size of the deposit. Greater changes occur in suspensions produced by emulsion and melt‐type formulations, than in those produced from wettable powder type formulations. The method of application—whether by dipping or spraying—and the breed of cattle used, also cause changes in deposition. It is concluded that the requirements for an optimal formulation for tick control could best be met by a flowable paste. Insolation resulting in decreased persistence of deposits is seen as the reason for the shorter protection against infesting ticks observed in summer. Fouling was responsible for most of the chemical decomposition which occurred in five of the acaricides studied.