A survey of medicinal herbs in markets of central and northern Mexico and southwestern United States revealed the existence of plant complexes of different species sharing common names, morphological and aromatic characteristics, and uses. Four complexes (with the "label" species listed first) discussed include: "cachani" with Roldana sessilifolia, Iostephane madrensis, Liatris punctata, Psacalium sp., and Potentilla sp.; "chuchupate" with Ligusticum porteri and Myroxylon balsamum; "hierba anís" with Tagetes lucida, T. filifolia, T. micrantha, Artemisia dracunculus, Pimpinella anisum, and Illicium verum; and "matarique" with Psacalium decompositum, P. peltatum, P. sinuatum, P. sp., and Acourtia thurberi. The distribution analysis of utilization and natural occurrence of plants in each complex indicated the presence of a dominant or "label" plant whose use extended beyond its natural range and which had substitutes derived from local plants that were not registered far beyond their respective natural ranges.