The biotransformation of neoandrographolide (1) was investigated by using Aspergillus niger (AS 3.739). Five products were obtained and identified as 8(17),13-ent-labdadien-16,15-olid-19-oic acid (2), 19-hydroxy-8(17),13-ent-labdadien-16,15-olide (3), 18-hydroxy-8(17),13-ent-labdadien-16,15-olid-19-oic acid (4), 3alpha-hydroxy-8(17),13-ent-labdadien-16,15-olid-19-oic acid (5) and 8beta,19-dihydroxy-ent-labd-13-en-16,15-olide (6) by spectroscopic and chemical means. Products 4, 5 and 6 are new compounds.