Laeviganoids A-T (1-20), 20 new ent-clerodane-type diterpenoids featuring a 2-furanone (1-3) or a furan (4-20) ring, as well as six analogues (21-26), were isolated from the roots of Croton laevigatus. Their structures were determined by spectroscopic data analysis, experimental electronic circular dichroism measurements, and X-ray crystallographic studies. Compounds 4-6, 16, 21-24, and 26 could influence the anti-inflammatory protumoral phenotype of macrophages. Among these compounds, 21 and 26 are the most potent, as evidenced by consistently downregulating the classic anti-inflammatory cytokine IL-10 and upregulating the classic pro-inflammatory cytokine TNF-α on the secretion level in RAW 264.7 cells.