Stephania japonica (Thunb.) Miens var. australis Hatusima, a taxon indigenous to the Ryukyu Islands (Japan), has an uncertain taxonomic position. The basic constituents of S. japonica var. japonica have been well studied, but the alkaloids of S. japonica var. australis have not been previously investigated. As a continuation of chemical studies on plants of the Menispermaceae, the alkaloids found in S. japonica var. australis were reported. Seven tertiary bases: hasubanonine, protostephanine, metaphanine, oxostephamiersine, thalrugosine, stephabyssine, an unknown base-A and two quaternary bases, cyclanoline and magnoflorine were isolated from a methanolic extract of stem and rhizome tissue. Of these alkaloids, hasubanonine, protostephanine, metaphanine, oxostephamiersine, cyclanoline and magnoflorine are common constituents of both varieties of S. japonica, but thalrugosine and stephabyssine have never been isolated from S. japonica var. japonica. On the other hand, the bisbenzylisoquinoline alkaloids epistephanine and hypoepistephanine, which have been identified in the variety japonica, were not found in var. australis. The unknown base-A was obtained as colourless prisms from MeOH, mp 248°C, C21H26O7NCl (M⁺, m/e 439.1392). Its IR spectrum showed absorption bands of OH group (3550 cm⁻¹) and γ-lactam (1683 cm⁻¹), and the ¹H NMR spectrum revealed signals due to four OMe groups (δ 3.42, 3.47, 3.84, 3.91), one NMe group (δ 3.09) and two aromatic protons (δ 6.72). In the MS spectrum, the most abundant and diagnostic peak appears at m/e 257.1068, indicating the pattern characteristic for hasubanan alkaloids. From these findings, it is suggested that this base is a new congener of the hasubanan series, the detailed structure of which will be made clear in future work.