Abstract A factorially designed set of 3-substituted 2-aryl-4, 5, 6, 7-tetrahydroindazoles was synthesized and their herbicidal properties were evaluated using regression analysis. For optimal activity, the substituent at position 3 should be neither strongly hydrophobic nor hydrophilic and should have a small minimum radius. A study of the mechanism of action indicated that the tetrahydroindazoles are inhibitors of the enzyme protoporphyrinogen ...