The present study describes methods to 1) selectively isolate Corn Cob Configurations (CCC) from dental plaque by micromanipulation; 2) obtain pure cultures of the coccal constituent; 3) determine by immunofluorescent procedure which organisms originated from the CCC. Using a de Fonbrune micromanipulator, CCC specimens were isolated from supragingival plaque samples. The viability of one specimen thus obtained was established by observing growth on a slide culture. One set of CCC specimens was transferred to broth and incubated aerobically immediately upon collection. Another set was transferred to prereduced transport medium and later plated on blood agar for aerobic and anaerobic culturing. A total of 10 coccal strains were thus isolated. Antisera produced in rabbits against the 10 strains were used to localize these coccal organisms on plaque smears by using the indirect fluorescent antibody technique. Of the 10 antisera tested, 2 produced against streptococcal strains consistently gave a positive immunofluorescent reaction with the coccal component of CCC in the plaque smears; the corresponding streptococci were therefore considered to be CCC forming strains in vivo.