The current study attempts to characterize the eosinophilia associated with T-cell lymphomas and to investigate its possible relationship with the secretion of eosinophil-stimulating factors by lymphoma cells and/or intra-tumoral surrounding cells. Paraffin-embedded specimens from 50 patients diagnosed with peripheral T-cell lymphomas, either unspecified (PTCL-U, n=30) or angioimmunoblastic (AITL, n=20) were morphologically assessed for intra-tumoral eosinophilia and analyzed by immunohistochemistry using specific antibodies directed against TARC, IL-5, RANTES, and eotaxin. The AITL and PTCL-U cases contained a mean of 147+/-41 and 102+/-37 eosinophils per 10 high power fields, respectively. Thirty-two of 47 cases (68%) showed IL-5-positive lymphoma cells while 15/50 (30%) tumors showed variable staining for TARC in scattered non-lymphoid cells with dendritic morphology. TARC and IL-5-positive cases possessed significantly more eosinophils. Our data indicate that IL-5 and TARC expression highly correlate with eosinophilia in T-cell lymphomas, suggesting that these chemokines are involved in the recruitment of eosinophils into the tumors.