Bioassay-directed fractionation of ethanolic extract of Kadsura matsudai Hayata has resulted in the isolation of four novel C(18) dibenzocyclooctadiene lignans, schizanrin B (1), schizanrin C (2), schizanrin D (3), and schizanrin E (4). Schizanrin B (1) showed moderate to strong activity for antihepatitis in both anti-HBsAg and anti-HBeAg assays, and 3 and 4 also were active in the latter assay [corrected]. Compounds 1--4 were inactive in vitro against HIV replication in H9 lymphocytes. All new structures were elucidated using spectral analysis. Their structural elucidation by spectral and structure--activity relationships is also discussed.