The advantages of Arabidopsis thaliana (L.) Heynh. for genetic studies are well known, but its diminutive stature and associated low biomass at maturity make it a challenging species for complementary physiological and biochemical studies. Hydroponic culture can significantly increase plant growth and produce uniform, stress-free root and shoot material that can be harvested throughout the life span of the plant. However, many shy away from the use of hydroponic culture because of the perceived difficulties in set-up and maintenance. Although other methods for the hydroponic culture of Arabidopsis have been reported (Rodecap et al., 1994; Delhaize and Randall, 1995; Hirai et al., 1995), they suffer from various shortcomings, including poor aeration, loss of root material, overcrowding, excess manipulation, and less-than-favorable environmental conditions. In this paper we describe an easy, low-maintenance method of hydroponic culture for Arabidopsis that combines the use of rockwool culture for uniform seedling establishment and a closed system of solution culture for the duration of plant growth. In addition, some consideration is given to temperature and light conditions that favor biomass production.The most difficult part of hydroponic culture for Arabidopsis is to rstablish a good root system, because young seedlings are prone to hypoxic stress from water logging. Rockwool (GrodanHP, Agro Dynamics, East Brunswick, NJ) provides an excellent, well-aerated rooting environment that is a far superior medium for reliable and uniform seedling establishment compared with other media we have tried, including cheesecloth, blue blotter paper, brown germination paper, filter paper, fiberglass matting, agar, and soil-or vermiculite-filled straws. Rockwool is a mixture of igneous rock and limestone that is heated and spun into mats. Even when saturated, rockwool holds about 15% air space.