This chapter deals with brassica plants and their resistance to sucking pests—aphids. Brassica plants are known to synthesize a number of plant secondary metabolites which impart resistance to insect-pests and diseases. Aphids are known to feed primarily on sieve elements. The sieve elements in vascular bundles of angiosperms are important channels for nutrition. They are the channels of transport of photoassimilates from source to the sink. Because of the high nutrition content of the sap inside sieve elements, they are the target for many insect-pests and bacterial and fungal pathogens. Aphids are one such group of insects which target SE elements of phloem for nutrition. They are among the most important insect pests in agriculture particularly serious in temperate and sub-tropical climates. In addition to direct damage by feeding as well as toxic effects of saliva, the withdrawal of nutrients is detrimental to plant growth and development. In addition to this, aphids also cause indirect damage to plants by acting as vectors of plant pathogenic viruses. Furthermore, honeydew excreted by aphids provides suitable substrate for sooty molds that interfere with normal plant photosynthesis. In this chapter work on host plant resistance in Brassica plants against aphids has been reviewed.