The production of kappa-carrageenase was studied in Pseudomonas carrageenovora strains NCIMB 302 and 9. The average specific production rate of kappa-carrageenase by strain NCIMB 302 on a semidefined yeast extract medium was found to be 15 times as high as in strain 9. A linear relationship was obtained for strain NCIMB 302 in batch fermentation between the kappa-carrageenase activity and the initial concentration of yeast extract. A similar linear correlation tvas also achieved for enzyme production on the kappa-carrageenan concentration. kappa-Carrageenan as an inducer could not be replaced by a low viscosity, low molecular galactose-containing carbohydrate. Supplying kappa-carrageenan by fed-batch addition prolongs the time of enzyme production to a small extent, but the observed enzyme concentration was not increased. Ar low values, a significant increase in enzyme activity was achieved with increasing casamino acid concentration up to 3.5 g l(-1), but the maximum activity decreased on further addition. When casamino acids were supplied as fed-batch, however, the production time was prolonged significantly and the enzyme activity increased 2.6 times up to 84,000 U l(-1) (observed) or more than four times lip to 136,000 U l(-1) estimated as volume-corrected values. Substituting the casamino acids by an equal amount of a single amino acid (glutamic acid), a similar enzyme production was obtained. The highest observed enzyme activity obtained here is 17 times higher than the values reported earlier (or 27 times higher when volume-corrected values are assessed).