Phytophagous insect faunas ofBaccharis salicinaTorr.&Gray,B. pteronioidesDC, andB. bigeloviiGray were studied in the southwestern United States and northern Mexico. Phytophagous insects representing 61 species, 31 families, and seven orders were collected onB. salicina.About 43% of these species were polyphagous; 13% were oligophagous, apparently restricted to the family Asteraceae; and 15% were monophagous, apparently restricted to the genusBaccharis.Sixteen percent of the insects collected were economically important pests. Phytophagous insects representing 55 species, 26 families, and seven orders fed onB. pteronioides.About 25% of the species were polyphagous, 13% were oligophagous, and 2% were monophagous. Phytophagous insects of 32 species, 22 families, and seven orders fed onB. bigelovii.About 28% were polyphagous, 16% were oligophagous, and 13% were monophagous. Months of the year that immature and adult insects were present on the host plant, relative frequency, and associated plant parts are reported.