Introduction. Among minimally invasive technologies for the treatment of stress urinary incontinence (SUI) in women, a special place is occupied by the method of paraurethral administration of bulking agents (BA). Recently, great attention has been paid to the new generation of natural biopolymers with a set of unique qualities that allow using the body's own resources to restore damaged tissues. Heterogeneous implantable gel (JSC «BIOMIR service», Russia) belongs to such BA. Objective: to evaluate the efficacy and safety of transurethral administration of BA «Sphero®GEL» LONG (SGL) in women with SUI. Materials and methods. The open prospective study included 20 women with mild or moderate SUI, aged 41-76 years, who underwent one/two transurethral implantation of SGL into the submucosal and muscular layers after clinical and urodynamic examination. Results. According to the preliminary survey, mild SUI was detected in 13 (65%) women, and moderate SUI – in 7 (35%). Initial data: visual analog scale (VAS) – 7.7 ± 2.0; quality of life (QOL) – 3.3 ± 1.2; maximum urine flow rate (Qmax) – 20.5 ± 5.3 ml/s; post-void residual urine volume (PVR) – 7.0 ± 2.1 ml; voided volume (VV) – 297.2 ± 65.6 ml; maximal cystometric capacity (MCC) – 312.1 ± 83.3 ml; maximum urethral closure pressure (MUCP) – 48.4 ±11.9 cm H2O; functional urethral length (FUL) – 20.3 ± 8.2 mm; one-hour PadTest 8.2 ± 1.9 g. Two weeks after the introduction of SGL, the satisfactory effect was detected in 17 women (85%) 6 of them (30%) were completely dry. The need for SGL additional administration occurred in 11 women (55%), which was fulfilled. There was an improvement in key parameters compared to the initial data 3 and 6 months after treatment: VAS index significant decrease by 70.1 and 63.6%; increase of MUCP by 8.9 and 7.9%; increase of FUL by 14.3 and 18.2%; statistically significant decrease of PadTest weight by 61.0 and 53.7%; improvement of QOL by 60.6 and 48.5%, respectively. There was a slight decrease in Qmax – by 11.2 – 8.3%. Changes in other indicators did not exceed normal values. When evaluating the results after 6 months in 17 patients (85%), the effect of treatment and the quality of life were assessed as satisfactory: according to PadTest results urine loss was less than 5 g. Moreover, in 11 cases (55%) urinary incontinence disappeared, so the full effect was achieved. There was no satisfactory effect in 3 women (15%), they were offered surgical treatment of SUI. Long–term results up to 12 months were followed in a group of 9 women with a good effect of SGL implantation. The dynamics of the main indicators a year after implantation was: 52.8% decrease according to VAS; 41.1% decrease according to PadTest; 48.3% of QOL improvement. SUI was also absent after a year of observation. Request for SGL re-administration was received from 3 of 8 women with unsatisfactory result, although their urine loss did not exceed 5 g per hour. No complications were observed during the SGL implantations. After the procedure urinary retention and the need for catheterization were not observed in any of patients. Allergic reactions, pain, severe hematuria, infection, tissue erosion at the injection site of SGL, as well as bladder overactivity «de novo» were not observed. Conclusion. The first experience of using the implantable heterogeneous volume-forming material SGL in women with mild and moderate SUI has confirmed the high efficiency of the technology, no worse than other samples of BA, with a high safety profile exceeding many of them. It is necessary to continue clinical research in this direction in order to implement the method into wide practice, also as part of import replacement activities.