Study question What are the reported data on cycles in ART, IUI and fertility preservation interventions in 2021 as compared to previous years and what are the main trends over the years? Summary answer The 25th ESHRE report on ART and IUI shows a progressive increase in reported treatment cycle numbers in Europe, a small decrease in the number of transfers (IVF + ICSI) with more than one embryo with a trend to decreasing multiple delivery rates, outcomes for IUI cycles are similar to previous years. What is known already Since 1997, ART aggregated data generated by national registries, clinics or professional societies have been collected, analyzed by the European IVF-monitoring Consortium (EIM) and reported in 23 manuscripts published in Human Reproduction and Human Reproduction Open. Study design, size, duration Yearly collection of European medically assisted reproduction (MAR) data by EIM for ESHRE. The data on treatments performed between January 1 and December 31, 2021, in 34 European countries were provided by either National Registries or registries based on personal initiatives of medical associations and scientific organizations. Participants/materials, setting, methods In all 1155 clinics offering ART services in 34 countries reported a total of 910 470 treatment cycles, involving 115 567 with IVF, 346 183 with ICSI, 311 487 with frozen embryo replacement (FET), 62 694 with preimplantation genetic testing (PGT), 69 883 with egg donation (ED), 246 with IVM of oocytes and 4410 cycles with frozen oocyte replacement (FOR). European data on IUI using husband/partner’s semen (IUI-H) and donor semen (IUI-D) were reported from 1242 institutions offering IUI in 29 and 21 countries, respectively. A total of 139 350 treatments with IUI-H and 45 532 treatments with IUI-D were included. A total of 28 692 fertility preservation (FP) interventions from 15 countries including oocyte, ovarian tissue, semen and testicular tissue banking in pre-and post-pubertal patients were reported. Main results and the role of chance In total, 1155 IVF clinics participated (81.4% of registered clinics in the participating countries). Next to these also 1242 IUI units reported their data. In the 34 reporting countries, after IVF the clinical pregnancy rates (PR) per aspiration and per transfer in 2021 were similar to those observed in 2020 (26.2% and 43.3% versus 25.4% and 40.9%, respectively). After ICSI the corresponding rates were also similar to those achieved in 2020 (23.9% en 45.7% versus 25.2% and 45.3%). Also after FET with own embryos, the PR per thawing is stabilizing, 35.0% in 2020 and 36.2% in 2021. After ED the PR per fresh embryo transfer was slightly increased to 53.1% (51.3% in 2020) and per FOR 45.5% (43.9% in 2020). In IVF and ICSI together, the trend towards the transfer of fewer embryos continues with the transfer of 1, 2, 3 and ≥4 embryos in 60.2%, 34.8%, 1.8% and 0.2% of all treatments, respectively (corresponding to 57.9%, 37.5%, 2.1% and 0.2% in 2020). This resulted in a proportion of singleton, twin and triplet DRs of 90.4%, 9.5% and 0.1%, respectively (compared to 88.9%, 10.9% and 0.2%, respectively in 2020). Treatments with FER in 2021 resulted in twin and triplet DR of 7.0% and 0.1%, respectively (versus 7.9% and 0.1% in 2020). After IUI, the DRs remained similar at 9.2% after IUI-H (8.8% in 2020) and at 14.0% after IUI-D (12.5% in 2020). Twin and triplet DRs after IUI-H were 7.4% and 0.2%, respectively (in 2020: 7.9% and 0.4%) and 5.9% and 0.2% after IUI-D (in 2020: 5.7% and 0.1%). The majority of FP interventions included the cryopreservation of oocytes (n= 11 966 from 15 countries) and of ejaculated sperm (n=14 688 from 15 countries). Limitations, reasons for caution As the methods of data collection and levels of completeness of reported data vary among European countries, the results should be interpreted with caution. For this abstract, some countries were not able to provide adequate data about the number of centers and initiated cycles and deliveries. Wider implications of the findings The 25th ESHRE report on ART and IUI shows a continuous increase of reported treatment numbers and MAR-derived live births in Europe. Being already the largest data collection on MAR in Europe, continuous efforts to stimulate data collection and reporting strive for future quality control and completeness of the data and offer higher transparency and vigilance in the field of reproductive medicine.