Three new system ic fungicides viz. A liette (efosite-Al), R id om il (m eta la xyl) and Ridom il MZ (metalaxyl plus m a ncozeb) were screened against two standard fungicides viz. Terrazole (etridiazole) and Difolatan (captafol) for prophylactic and therapeutic effica cyagainst Phytophthora palmivora on orchids. Terminal shoots o f Aranda Christine hybrids were e ffe c tiv elyprotected from Phytophthora in fection when sprayed with metalaxyl at 0.05% a.i., m e talaxy l-mancozeb m ix tu r e at 0.15% a.i. and captafol at 0.2% a.i. three days before artificial inoculation. Etridiazole and efosite-Al, b oth at 0.1% a.i. did n o t give adequate protection. Metalaxyl (0.05% a.i.) and its mixture with mancozeb (0.15% a.i.) retarded significantly disease development by Phytophthora when used as a curative spray. Etridiazole (0.1% a.i.) and e fo site -A l (0.1 a.i.) gave moderate therapeutic co n tro l while captafol gave no therapeutic control. No p h y to x ic ity was observed with Ridomil MZ, Terrazole and A lie tte up to concentrations o f 0.5%o a.i., 0.4%> a.i. and 0.8 a.i. respectively. The R id om il products, A liette and Terrazole e xh ib ited similar rates o f inhibition o f linear extension of P. palmivora b ut differed in the degree o f in vitro fu n g ito x ic ity . The Ridomil products and Terrazole had EDso values o f less than 1 p g /m I while Difolatan was relatively less to x ic (EDSy) 19.9 µ l / l).