The effects of glucose, osmolarity, temperature and mode of growth on exopolysaccharide production in Pseudomonas cepacia was studied in batch culture using a chemically defined growth medium. Polymer production was maximal under conditions of a 2% (w/v) glucose supplement, 0.4 M NaCl and an incubation temperature of 35 degrees C. In addition, polysaccharide composition and molecular weight varied with mode of growth. On agar culture there was a decrease in pyruvate and rhamnose content yet an increase in the amount of acetate compared to the polymer isolated from broth culture equivalents. The clinical implications of these results are discussed in relation to the potential pathogenicity of P. cepacia in cystic fibrosis patients.