Recent studies prove that cryptococcal disease is widespread1-5 and although amphotericin B is recommended for the treatment of disseminated cryptococcal disease,6,7 the critical decisions of (1) who and when to treat,8,9 (2) rate of administration, and (3) duration of therapy are often difficult or impossible to evaluate objectively. Our experience with a patient who had severe meningocerebral and pulmonary cryptococcal infection made increasingly apparent the value of laboratory tests in the diagnosis and treatment of severe Cryptococcus neoformans infections. Confirmation of a disseminated infection was made by the latex agglutination test,10 using both serum and cerebrospinal fluid (CSF). The rate of administration of amphotericin B was regulated by measuring inhibition of the organism by serum and CSF during therapy.11 The effectiveness of this chemotherapy and an estimate of the prognosis were determined by measuring cryptococcal antibody and antigen concentrations in the serum and CSF of