6 newly synthesized metalaxyl analogs were studied in laboratory and field tests with sensitive and resistant populations of Phytophihora infestans. Field studies were carried out simultaneously on preparations containing phenylamid and copper oxychloride. Ridomil 25 WP (metalaxyl) and Ridomil Plus 45 WP (metalaxyl plus copper oxychloride) were adopted as standards. It was stated that all metalaxyl analogs in laboratory tests on sensitive populations of Phytophihora infestans did not differ significantly in activity in comparison with metalaxyl. But the analogs efficacy tested on the resistant population was lower in comparison with metalaxyl which activity against resistant populations also decreased apparently. The mixtures of metalaxyl analogs showed similar activity to the standard Ridomil plus 45 WP.