2-Amino-4- or 6-(trifluoro- or chlorodifluoromethoxy) pyrimidine derivs. of formula (I) are new, where R1 = H, 1-4C alkyl, 3-4C alkenyl or 3-4C alkynyl; R2 = H, halo 1-4C haloalkyl, OCF3 or OCF2Cl; R3 = H, halo or 1-4C haloalkyl; n = 0 or 1; m = 2 or 3; m+n = 3. 2-Amino-4-X -6-trifluoromethoxy -pyrimidine (X = F or Cl); 2-amino-4-chloro difluoromethoxy-6 -fluoro-pyrimidine; and 2-amino-4-chloro -6-chlorodifluoromethoxy -pyrimidine are specifically claimed. -