Strains of Neisseria gonorrhoeae were inoculated onto brain heart infusion (Difco) agar supplemented with penicillin and polyvinylpyrrolidone (PVP) as a stabilizer and cultivated in a candle extinction jar. L-form colonies became visible after a few days. They continued to grow and were viable for up to 38 days. The extent of inducibility of L forms of N. gonorrhoeae was examined semiquantitatively. It was found to be constant for each type and strain and to depend only slightly on the amount of penicillin added to the medium. None of the types of one strain produced L-form colonies. In another strain, avirulent types (T3, T4) showed more ability to produce L forms than virulent types (T1, T2) and no L forms were produced by the subtypes of T1 and T2-T1a and T2a. In a third strain, only T4 produced L forms. Electron microscopic studies showed that the L forms consisted of a number of membranous vesicles and a variety of cell types such as those completely lacking cell walls and those with only remnants of cell walls. The results indicate the existence of subtypes of T1 and T2 of gonococci and the intrinsic inducibility of gonococcal types and strains to produce L forms.