Specific immunotherapy (SIT) can in some cases influence the course of allergic inflammation (eosinophilia and ECP concentration in peripheral tissue). This study was set up to evaluate the efficacy of three-year pre-seasonal SIT with grass pollen allergoid. We measured NALf eosinophilia and ECP concentration both in NALf and blood serum after subsequent SITs. Twenty seven patients aged 26.7 +/- 7.4 (range 18-45) entered this study. They were randomly assigned to treatment with either Pollinex or Allergovit. We observed a progressive fall in NALf eosinophilia in subsequent years: 24.1 +/- 2.4%; 20.2 +/- 4.6%; 9.8 +/- 1.9% vs. 30.4 +/- 3.0% before treatment (p < 0.05, p < 0.05 and p < 0.001, respectively). Also ECP concentration fell after second and third SIT to 15.6 +/- 1.5 ng/ml i 12.96 +/- 1.75 ng/ml vs 23.3 +/- 3.7 ng/ml before SIT (p < 0.05). A significant drop in serum ECP concentration was recorded only after the third SIT season--2.5 +/- 1.23 micrograms/ml vs 5.8 +/- 1.3 micrograms/ml before treatment, p < 0.01. NALf eosinophilia correlated positively with NALf ECP concentration--R2 = 0.92, p < 0.05. Hence, SIT ameliorates allergic inflammation decreasing significantly activity of eosinophils in nasal mucosa measured as NALf eosinophilia and ECP concentration. This effect seems to be time-depended.