||1. A new system of chromatography has been described which allows resolution of the less polar steroids" such as cholesterol and congeners. It is a reversed phase system utilizing odorless kerosene as the stationary phase, and 60 per cent aqueous n-propanol as the developing phase. It has proved extremely useful in separation of "fat" and other unwanted compounds from more polar ones for which further resolution is desired. 2. A new color reagent, phosphotungstic acid, has been presented. It has proved useful in the location and identification of certain steroids having a delta4,3-ol or a delta5,3-ol grouping. 3. Incubation of preparations of testes from hypophysectomized rats treated with human chorionic gonadotropin have shown a correlation between the amount of gonadotropic stimulation, as indicated by the reversal of atrophy of the seminal vesicles, and the amount of conversion in vitro by the testes of progesterone-21-C14 to C19 androgens. 4. Testis tissue from normal immature rats treated with HCG has shown a much higher capacity (4-5 times) to convert progesterone to androgen than testis tissue from hypophysectomized rats similarly treated. 5. During the conversion of progesterone-21-C14 to C19 androgen, a radioactive acid was produced. It has the distillation characteristics of formic acid or acetic acid but appears to be neither as indicated by isotope dilution experiments. The chemical identity of the acid remains unknown. 6. It was shown that rat testis tissue was able to convert 17alph-hydroxy-progesterone to androstenedione and testosterone. Whether 17-OH-P is an obligatory intermediate in the conversion of progesterone to C-19 androgens has not been determined with certainty, but it would seem to be so. 7. The data of these experiments indicate that androstenedione is the first C-,q compound produced from a C19 compound and that testosterone arises from reduction of androstenedione. Testis tissue was shown to be able to inter-convert androstenedione and testosterone with a dependence of mediation by phosphonucleotides. 8. Production of both androgen and 17alpha-hydroxyprogesterone from added progesterone and conversion of added 17-OH-P to androgen was blocked when a nitrogen atmosphere replaced oxygen in the incubation flasks. It was considered that 17-OH-P is probably not converted to androgen by simple one-step hydrolysis as originally postulated. Conversion in the presence of a nitrogen atmosphere was accomplished by both a testis homogenate and a testis microsome preparation when ascor-bate was added to the incubation medium also containing TPN, fumarate, and ATP. The role of ascorbate is unknown. 9. Added DPN and TPN were necessary for conversion of progesterone and for conversion of 17alpha-hydroxyprogesterone by homogenates. TPN was more effective than DPN in the total conversion of progesterone while DPN and TPN were equally effective in the conversion of 17alpha-hydroxyprogesterone. It is postulated that TPN is a cofactor in the synthesis of 17alpha-hydroxyprogesterone. 10. Inhibition of the conversion of progesterone was accomplished by the inclusion of mercuric ion in the incubation medium. Inhibition was also obtained by the inclusion of arsenite. It is suggested that lipoic acid might be involved in the scission of 17alpha-hydroxyprogesterone to produce C19 androgen. 11. The intracellular enzymes responsible for the production of androgens from progesterone seem to be located in the microsomes. Non-involvement of the mitochondria was not established, however.