Eosinophilia occurs in up to 75-90% of nasal polyps in Caucasians. The chemokines eotaxin and RANTES increase eosinophil recruitment, activation, and survival, and these chemokines are significantly expressed in nasal polyps. We hypothesized that eotaxin and RANTES plasma levels might be correlated with disease severity. We compared the eotaxin and RANTES plasma levels in 20 Taiwanese patients with chronic rhinosinusitis and nasal polyps and 20 Taiwanese healthy controls. Eotaxin and RANTES plasma levels were measured by ELISA and disease severity was scored by CT scans. Compared to controls, patients with nasal polyps had significantly elevated plasma levels of eotaxin and RANTES and increased peripheral blood eosinophils (p < 0.001). Eotaxin plasma levels were significantly correlated with disease severity in patients with chronic rhinosinusitis to a greater extent than were RANTES levels. RANTES and eotaxin levels were also positively correlated with the percentages of peripheral blood eosinophils. Eotaxin plasma levels are significantly correlated with disease severity in Taiwanese patients with nasal polyposis to a greater degree than are RANTES levels. Additional studies are needed to assess whether eotaxin plasma levels can be used to monitor disease progression and attenuation.