Aim — to evaluate the clinical effectiveness of crosslinking in patients with progressive pellucid marginal corneal degeneration (PMCD). Material and methods. A total of 9 patients (16 eyes) with progressive PMCD were treated by standard crosslinking. The cornea was saturated with Dextralink solution and UV-A irradiated at 3 mW/cm2 for 30 minutes. The follow-up period was 12 months. Results. One month after treatment, there was a slight decrease in uncorrected and best corrected visual acuity (UCVA and BCVA) — from 0.08±0.03 and 0.4±0.15 preoperatively down to 0.06±0.02 and 0.3±0.07, respectively, caused by pseudohaze of the cornea. Keratometric parameters (the average refractive power of the cornea, corneal astigmatism, and corneal thickness) did not change significantly. The demarcation line was identified in 56% of cases. By the 3-month follow-up, UCVA and BCVA improved up to 0.1±0.07 and 0.52±0.1, respectively. The refractive power of the cornea decreased by 2.0 diopters and corneal astigmatism — by 0.7 diopters reaching 46.8±2.7 and 5.1±1.3 diopters, respectively (p≤0.04). Central corneal thickness decreased by an average of 29 microns. The demarcation line remained visible in 25% of cases. At 6 months, BCVA averaged 0.58±0.13, at that, 56% of eyes gained 1 line and 31% — 2 lines. The refractive power of the cornea decreased down to 45.7±1.6 diopters, corneal astigmatism — down to 4.8±1.5 diopters. The demarcation line was not detected. At 1 year, there were no significant changes in the average values of optometric indices as compared to the 6-month period. Сonclusion. Pellucid marginal corneal degeneration should be regarded as a kind of primary ectasia, often bilateral and notable for its characteristic clinical picture and late onset. In progressive disease, photochemical crosslinking of the cornea contributes to the improvement of optometric parameters and stabilization of the process.