Nonclassical 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase deficiency (NC3 beta HSDD) has been diagnosed in hyperandrogenic women with an increasing frequency during the last 14 yr. Fifteen menarcheal women with androgen excess syndrome, diagnosed with NC3 beta HSDD previously were restudied, in 12 after discontinuation of glucocorticoid treatment, in 2 patients never treated with glucocorticoids, and in 1 both before and after glucocorticoid therapy. Each of the 15 patients underwent ACTH stimulation testing, in some cases on multiple occasions. Although some (very few) patients seem to have improved with time, others remained the same or got worse. Molecular DNA analysis was also performed in 6 of the patients, using the strategy successfully used to detect point mutations in the type II 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) gene, which are responsible for classical 3 beta HSD deficiency. This strategy consists of the direct sequencing of polymerase chain reaction-amplified DNA fragments corresponding to the complete coding sequence and all intron-exon junctions and to the 5'- and 3'-noncoding region of this gene. We were unable to demonstrate any mutation of the type II 3 beta HSD gene in these 6 patients. To gain additional information about potential mutations, direct sequencing of the type I 3 beta HSD gene was also performed using this same strategy, and no mutations were found. The present study strongly suggests that unlike the salt-losing and nonsalt-losing forms of classical 3 beta HSD deficiency, NC3 beta HSDD is not due to a mutant type II 3 beta HSD enzyme. However, the possibility remains of a mutation(s) in the unsequenced regions of the type II 3 beta HSD gene or elsewhere, such as in a gene for modulatory protein, playing a specific role in the expression of the type II 3 beta HSD gene. On the other hand, knowing the multiple hormonal controls to which 3 beta HSD activity is subject, it cannot be excluded that at least in some cases, NC3 beta HSDD may be an acquired defect, the result of endogenous or environmental factors.