Formulation of culture media using potato,tomato, and fish emulsion as basic components and 13inorganic salts as supplements were made for growingorchids in vitro. A total of 62 new formulations andthree know formulae were used as controls. A selectionof media was made on good typical growth of thegerminating seeds, young seedlings, and callusformation from seeds or buds from young shoots of themembers of Dendrobium. A group of selected media whichsupported good to very good growth was used for furthertests on other genera. The genera used in testing wereCattleya, Rhynchostylis, Spathoglottis, Vanda andVandopsis. The media containing three organic components and13 inorganic salts gave much better results in seedgermination and seedling growth of Dendrobium than themedium made basically with inorganic salts. A group ofthe selected media comprising ones with only organiccomponents and the others with different combinationsof organic and inorganic components were used in seedgermination of Rhynchostylis, Vanda, Vandopsis and therearing of the seedlings of Vanda. The results obtainedin these genera were very much the same as the genusDendrobiurn. However, much deviations were found inother genera. In a medium containing only three organiccomponents, seed germination and seedling growth ofCattleya exceeded all other media tested. Fresh weightof 4 month old seedlings was at least five times of theones grown in the inorganic medium (control). Similarresults were observed in the culture of Rhynchostylisseedlings. Unexpected result was discovered during seedgermination of Rhynchostylis. Most of the seedsproliferated into callus masses without adding anyregulator. Some members of Spathoglottis could not producenormal growth in the media containing organiccomponents mentioned above. The parts that contactedthe media were damaged by phenolic compound or similarsubstances which interfered with the absorption ofnutrients from a medium. Since Orchidaceae is one of the largest family inthe plant kingdom, it is expected to have greatbiodiversity in all aspects. Therefore, physiology ofseed germination and seedling growth in expected to bespecific for a given group of orchids. Twenty differentmedia are recommended for these purposes.