The title compound, 1-(2′, 3′-dideoxy-β-d-glycero-pent-2-enofuranosyl) thymine 1-methyl- 2-pyrrolidone solvate, C10H12N2O4· C5H9NO, is an NMPO solvate of the anti-AIDS agent D4T. In its crystal structure, both the pyrimidine and the furanose rings are planar and approximately perpendicular [82.1 (4)°]. The value of the torsion angle defining the orientation of the thymine with respect to the joined furane, χ=− 100.8 (4)°, and that of the ...