Direct on-line studies of a C2HCl3/He/O-2 microwave discharge plasma made possible the evolution and detection of many unfamiliar ionic species. Numerous ionic chlorocarbons, chlorohydrocarbons, oxygenated chlorohydrocarbons, oxygenated hydrocarbon radicals, and simple hydrocarbon species were identified mass spectrometrically as by-products: C (m) Cl (n) (m = 1-4, 6, 8; n = 1-8), C (m) H (n) Cl (x) (m = 1-4, 6, 7, 10; n, x = 1-6), C (m) H (n) Cl (x) O (y) (m = 1-5, 12; n = 1-7; x = 1, 2, 4, 6; y = 1-3), C (n) H2n-1O (n = 2, 3), C (m) H (n) (m = 2, 4, 6, 8; n = 2, 4), and so on. The studies clearly showed the presence of various unfamiliar positive ionic O-containing species such as C2ClO2, CCl3CO, C2H2Cl4O2, and C4H2Cl6O3. It is apparent that positive-ion reactions play a significant role in producing many ionic species in the chemistry of C2HCl3 plasmas.