Clara cell 10-kD protein (CC10) is a multifunctional protein with anti-inflammatory and immunomodulatory effects. In this study we evaluated the dosage effects of recombinant human CC10 protein (rhCC10) on modulation of protein secretion in human airway epithelial cell line Calu-3. Our methodology involved testing the effects of various concentration of rhCC10 (0.5, 1.5 and 5 mg/ml) on Calu-3 cells grown at an air-liquid interface under hyperoxia insult for 24 and 48 hr. The total protein, interleukin-8 (IL8) and interleukin-6 (IL6) were measured in Calu-3 apical surface secretions by collecting apical surface fluid washings (ASF) with sterile water. Our results showed that 5 mg/ml of CC10 treatment exhibited a significant increase in total protein secretion after 24 and 48 hr under both normoxic and hyperoxic conditions. When Calu-3 cells were treated with CC10 basolaterally, a decreasing trend in total protein was observed in ASF washings indicating apical and basolateral treatment with rhCC10 exert opposing effects in protein secretory pattern. We next examined the levels of major inflammatory mediators IL-8 and IL-6 in Calu-3 protein secretions. Our results demonstrated a significant decrease in IL-8 under hyperoxia after 48 hr of CC10 treatment, whereas a steady increase in IL-6 under all conditions. These in vitro studies suggest that CC10 modulate protein secretion and inflammatory mediators in airway epithelial cells and that IL-8 and IL-6 are significantly modulated under hyperoxic insult.