While there is considerable evidence that certain of the nasopharyngeal Neisseria spp. may under favorable conditions give rise to meningitis, the patho-genicity of the capsulated diplococci for man has not been proved. A case is reported in which the causative organism was almost certainly Diplococcus mucosus. The cerebrospinal fluid was turbid, with 330 cells per c. mm.; mainly polymorphs; protein 240 mg.%. Fair numbers of Gram-negative diplococci were present, sometimes intracellularly. The opposed sides of the cocci were flattened, but they were larger and more irregular than meningococci. Culture of the-deposit on blood agar aerobically produced in 24 hrs. a profuse growth of yellowish mucoid colonies consisting of encapsulated Gram-negative diplococci. Sulfapyridine was given by the mouth, the initial dose being 2 gm. Oral adm. was satisfactory, and 9 gm. were given in the first 24 hrs. The patient rapidly became quieter, and the temp. fell to 99.4[degree] F. The general condition was better, the headache less severe, and the mental state normal. The rash had almost completely faded, but petechiae were noted on the anterior aspect of the legs and there was a circular purpuric patch an in. in diameter on the right calf. Ptosis persisted and neck rigidity was still present, but Kernig''s sign was neg. Lumbar puncture again yielded a turbid fluid; the pressure was normal. Sulfapyridine was continued in a dosage of 1 gm. every 4 hrs. Improvement continued, and during the next few days the rigidity, ptosis, and headache abated. The dosage of sulfapyridine was decreased and the drug was discontinued, a total of 22 gm. having been given.