Various species of ticks collected from different regions of Tanzania were tested for susceptibility to organochlorine (OC) acaricides between 1976 and 1987 using gamma HCH (lindane) and dieldrin as standard test chemicals. Of 189 strains tested, 85 (45%) had developed resistance to these chemicals, viz.Boophilusspecies (36.5%),Rhipicephalus appendiculatus(3.5%),R. evertsi(41.2%) andAmblyomma variegatum(3.5%). In an earlier survey carried out between 1973 and 1976, resistance was found in the following number of strains:R. appendiculatus(1),R. evertsi(3) andA. variegatum(1);Boophilusspecies were found to be resistant countrywide. Although the current survey indicates a marked increase in resistance, OC‐resistantR. appendiculatusthe sole vector of East Coast fever of cattle, still exists in the Kagera Region only. OC acaricides could therefore continue to be used for tick control on indigenousBos indicuscattle in all regions of Tanzania where resistant R.appendiculatusis not present.