Eighteen N-substituted phenyl 1, 3, 5-trimethylpyrazole-4-carboxamides were synthesized to screen for their mycelial growth inhibition activity against Rhizoctonia solani Ku¨hn (pEC_(50)) and to measure enzymatic inhibition activity of these compounds (pI_(50)) against succinate dehydrogenase (SDH) isolated from R. solani Ku¨hn. A structure-activity relationship formulated by regression analysis showed that 79% of the variance in mycelial growth inhibition activity can be explained with SDH inhibition activity and chromatographic capacity factor (k`) as a hydrophobic parameter related to the penetration and transport processes in the biological system.