This article describes the major results of exploring the contemporary American English particulars of rhythmical groups’ structural types quantity distribution as observed in the course of impromptu speaking and compared with extemporaneous reading, subject to the speaker’s gender. A number of specific features relating both to gender and oral speech production form are discussed. It was found that when switching to impromptu speaking both gender groups show an increase in the number of rhythmical groups of all structural types, however, the specificities of such an increase are different in either group. Women showcase an approximately twofold total gain in the number of rhythmical groups than men. Against the background of the general increase in the number of rhythmical groups of all structural types in a phrase, the Stress Rhythmical Group’s percentage share dynamics in the total gain turned out negative being the only negative indicator for men. With women the negative percentage share dynamics in the total gain is observed in rhythmical groups of two structural types: the Stress and the Proclitico-Enclitic ones. It is noteworthy that both gender groups attest to the same value of the aggregated negative percentage share dynamics in the total gain in the number of rhythmical groups which is equal to -0.8%. The major driving force of the gain in the total number of rhythmical groups is the Enclitic type. However, women evince an approximately 1.5 times greater percentage share dynamics in the gain of the Enclitic rhythmical group than men. Men compensate the reduced Enclitic rhythmical group gain percentage share dynamics by an increase of the indicator in such types as Proclitic and Proclitico-Enclitic. The most rigid structural type of rhythmical groups for women is the Proclitic one, it is also the least numerous for both genders. However, with men, the Proclitic rhythmical group is as agile as the Proclitico-Enclitic one provided, when the latter can be observed almost four times more often than the former. The author makes a number of assumptions and develops several hypotheses about the reasons for these observations, as well as draws possible perspectives for further studies.