The constituents of a normal monoecious fig, namely the male and female flowers, the short-and long-styled female flowers and the male and female wasp galls, are arranged in definite spatial and numerical relations. The normal development of the syconium depends on a balance of these different elements. Occasionally various types of aberrant figs are found in nature, differing from normal figs in development and in final structure. These are purely gall figs, seed figs and male wasp or female wasp figs. Such abnormal figs were obtained experimentally by introducing specially treated female wasps into receptive young syconia at the receptive B phase. Treatments of the wasps involved one of the following: shortening of their ovipositor, preventing contact of wasps with pollen, preventing wasp fertilization or their sterilization by irradiation with gamma rays at various doses. In some of the already inhabited figs, the wasp larvae were killed by insecticidal sprays. Analysis of the development and structure of naturally-found aberrant syconia, taking into account also the conditions under which they may be produced experimentally, provides data for elucidating various aspects of the mutualistic symbiosis in figs.