[en] This paper describes the results of a study of the effect of the bacterial polysaccharide prodigiosan and the yeast cell membrane bipolymer zymosan on the absolute and relative levels of cAMP, cAMP, and cAMP-dependent phosphodiesterase (PDE) in the thymus, spleen, and lungs of healthy mice and of mice with metastasizing Lewis' lung carcinoma. The cyclic nucleotide concentration was determined by radioimmunoassay. Radioactivity of the samples was studied in an SL-30 liquid scintillation counter. PDE activity was determined by paper chromatography using 8-³H-cAMP as the substrate