Atrazine, metribuzin, alachlor, metolachlor, and cyanazine are herbicides frequently implicated in groundwater and surface water contamination. These herbicides were microencapsulated within six different polymers by the solvent evaporation process using two different emulsifiers. Efficacy studies on various weed species were conducted under greenhouse conditions. Overall, nine of the twelve atrazine formulations were at least as effective as a commercial dry flowable formulation and five exhibited superior herbicidal activity and controlled-release properties for 32 weeks after treatment. Five of the twelve metribuzin formulations exhibited controlled release properties, but were not quite as effective as the commercial formulation. The most efficious polymers were cellulose acetate butyrate and ethyl cellulose. Alachlor and metolachlor formulations prepared with cellulose acetate butyrate and ethyl cellulose were comparable (in a few instances superior) to the commercial formulation in activity, whereas those prepared from low and medium molecular weight poly(methyl methacrylate) exhibited little herbicidal activity. In studies of polymeric formulations of atrazine, metribuzin, alachlor, and metolachlor, microcapsules prepared with poly(α-methylstyrene) initially exhibited high activity, but activity dropped dramatically after four or eight weeks. However, poly (α-methylstyrene) formulations of cyanazine consistently showed the greatest efficacy, comparable to the commercial formulation, along with one ethyl cellulose formulation.