Among proteins secreted from activated eosinophil granulocytes, eosinophil cationic protein (ECP) is the most useful tool for the follow-up of inflammatory diseases. Since ECP level reflects the eosinophil activation, it gives valuable information about disease activity. In this study, we aimed to investigate the possible relation between ECP levels and symptoms and laboratory findings of cystic echinococcosis (CE) and to evaluate the role of this protein in the diagnosis of CE. The study which was conducted at Clinical Microbiology Laboratory of Suleyman Demirel University Medical Faculty, Isparta, Turkey, included 58 patients with a pre-diagnosis of CE and 32 healthy individuals as control group. The diagnosis of CE was established serologically by modified enzyme-linked immunosorbent assay (ELISA) and indirect hemagglutination (IHA) test. The quantitative determination of ECP levels was done by fluoro-enzyme immunoassay (FEIA; Uni-CAP ECP, Pharmacia-Upjohn). The mean ECP level was 31.6 +/- 37 mu g/ml in the patient group and 9.1 +/- 2.1 mu g/ml in the control group, the difference being statistically significant (p= 0.001). Significant differences were also detected for erythrocyte sedimentation rate (ESR) (p= 0.001), total IgE level (p= 0.001), eosinophile count (p= 0.05) and CRP (p= 0.001) between the patient and the control groups. ECP was detected to be high in 35 (60%), IgE in 37 (63%), CRP in 29 (50%) and eosinophile count in 9 (15.5%) patients. While age, gender, ESR, IgE and CRP levels of patients with high ECP levels were not significantly different from levels of patients with normal ECP levels, significantly different eosinophil counts were detected among patients with high ECP values when compared to patients with normal ECP values. Furthermore, a correlation was detected between ECP levels and eosinophil rate, IgE and CRP levels of patients with CE (p= 0.01), while there was no correlation between ECP and ESR levels. Although high ECP level patients exhibited higher ALT and AST levels, no correlation was determined between liver enzyme levels and ECP levels (p> 0.05). The most common symtoms among CE patients were abdominal pain (41%), other gastrointestinal complaints (38%), shortness of breath (12%) and fever (10%). No statistically significant difference in terms of symptoms was detected between patients with high ECP levels and normal ECP levels. However, statistically significant difference was detected between ECP levels of patients with symptoms (except shortness of breath) and patients without symptoms (p< 0.05). In conclusion, ECP seems to be associated with the symptoms and signs of CE and it can be used as a valuable marker besides the other laboratory tests for the evaluation of patients with CE.