The market for mushrooms continues to grow due to interest in their culinary, nutritional, and health benefits. Mushrooms contain many essential amino acids; white button mushrooms, for example, contain more protein than kidney beans. Shiitake mushrooms are less nutritious, but are still a good source of protein (Royse and Schisler, 1980). As a group, mushrooms also contain some unsaturated fatty acids, provide several of the B vitamins, and vitamin D. Some even contain significant vitamin C, as well as the minerals potassium, phosphorus, calcium, and magnesium (Park, 2001). However, as fungi, mushrooms have life cycles very different from those of green plants. Mushrooms do not contain chlorophyll and therefore depend on other plant material (the "substrate") for their food. The part of the organism that we see and call a mushroom is really just the fruiting body. Unseen is the mycelium, tiny threads that grow throughout the substrate and collect nutrients by breaking down the organic material. This is the main body of the mushroom. Generally, each mushroom species prefers a particular growing medium, although some species can grow on a wide range of materials. The choice of species to be raised depends both on the growth media available and on market considerations. Oyster mushrooms, which grow on many substrates, are easiest for a beginner. Shiitake mushrooms already have earned considerable consumer demand. Small-scale mushroom production represents an opportunity for farmers interested in an additional enterprise and is a specialty option for farmers without much land. The goal of this exercise is to start with one mushroom fruiting body and turn it into a bunch of new fruiting bodies. There are two mechanisms by which mushrooms can reproduce -- by spores or by propagation of tissue extracted from a fruiting body. We will use the latter technique, which is simpler and which offers a better chance of success for the beginning cultivator. There are three distinct phases (fig 1) through which your culture will pass: 1. Sterile culture on an agar medium 2. Sterile culture on grain, also known as "grain spawn" 3. Fruiting on a pasteurized substrate