Four greenhouse experiments were conducted in 1994 and 1995 to evaluate the effects of physical properties of soilless media on seedling production in the float system. Ten media were prepared in 1994 and five in 1995, from various combinations of peat, vermiculite and perlite. A particle size distribution was determined for each media treatment. Two experiments were conducted in 1994 with flue-cured tobacco to examine the effects of each medium on seedling production in two cell sizes (27cc and 17cc) and at two packing levels (normal and 2X normal). In 1995, the packing study was repeated with flue-cured and Burley cultivars; and another experiment examined fertilization levels and the accumulation of soluble salts in each of five prepared media. Acceptable seedling production was obtained in all but the 100% peat and the 50% peat 50% perlite treatments. A positive correlation was observed between seedling emergence and the percentage of particles in the 0.355-1.4mm range. Dry cell incidence was greatest in media with the greatest percentage of particle sizes above 2mm. Twice-normal packing increased the incidence of negative geotropism in all media. Fertilizer salts accumulated to dangerous levels in the upper portion of the cell in all media treatments.