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The economics of utilizing rice straw for energy, animal, chemical and construction material production are dependent on the yields and properties of the input straw. Variations in rice straw availability and quality can have critical effects on these biomass production systems. To generate better information on this variability, variety trials were planted for the 1999 and 2000 seasons. Eight common California rice cultivars were grown and harvested at two sites each. Total straw yields varied from 7.0 Mg/ha to 13.6 Mg/ha with an average of 9.8 Mg/ha. Straw-to-grain ratios varied widely from 0.89 to 2.29 with an average of 1.27. The distribution of the biomass in the plant was quantified from field samples and a yield model based on the plant cutting height is proposed. Samples of the major varieties were also analyzed for structural properties and ash content. Straw-to-grain ratios seem to be more influenced by season than by variety and location. This means that grain yield may not be a good indicator for available straw. The property analysis reveals similar compositions across the study variables. The one exception is that silica ash is more highly concentrated in the plant leaf than the stem with silica being 15% of dry matter in the leaf while only 5% of the stem. Since silica is undesirable to many of the industries using rice straw, there may be ways to take advantage of this through processing or development of new cultivars.