Since the identification of 17a,20ß-dihydroxy-4-pregnen-3-one (DHP) as the main maturation-inducing hormone (MIH) in Japanese eel A. japonica, female European eels have been injected with this steroid to induce oocyte maturation and ovulation. However, the females injected with DHP need to ovulate rapidly following the DHP injection to release good quality eggs. In this study, we compared treatment of progesterone (P) with DHP treatment as control, in vitro, to determine dose-response effects, and in vivo, at a single dose. Females were first matured by the routine protocol of weekly injections with carp pituitary extract (CPE at 20 mg kg-1) until a significant oocyte hydration response occurred as indicated by an increase of the body weight and oocytes displaying germinal vesicle migration. For the in vitro experiment, ovarian tissue was extracted and placed in culture plates containing hormone-free medium and media supplemented with the treatment (P: 10, 100, 1,000 ng.mL-1 DHP: 1, 10 and 100 ng.mL-1). Before and after incubation for 12 and 18 h, the folliculated oocytes were sampled for microscopy and gene expression analysis. For the in vivo experiment, females were either injected with P or DHP at a dose of 2 mg.kg-1 to assess their effects on ovulation and reproductive success. At the moment of stripping, eggs were sampled for RNA-sequencing to compare P vs. DHP stripped eggs with focus on genes marking gamete quality. Remaining eggs were fertilized and larval viability was recorded. Both P and DHP were able to induce germinal vesicle breakdown in vitro (P at 100 and 1,000 ng mL-1 DHP at 10 ng and 100 ng mL-1). RNAseq results reflected similar P and DHP effects on the expression of genes involved in egg quality aspects. Also expression of genes involved in oocyte maturation and ovulation was similar for both P and DHP treatment. Females injected with either P or DHP ovulated, released eggs and were equally able to produce larvae without any differences in reproductive success. Our results support the conclusion that P and DHP have similar competence as MIH which may be because P binds to the membrane progestin receptors with similar capacity as DHP does. P is more attractive to apply as the price is 3,000 times lower than the price of DHP. Overall design: Differential gene expression analysis of RNA-seq data (all samples in triplicate) for control oocytes before DHP and progesterone treatment and eggs harvested after either DHP or progesterone treatment.