The aim of this study was to investigate the value and significance of interleukin-8 in differentiation of uncomplicated parapneumonic effusion (UCPPE) from complicated parapneumonic effusion (CPPE). Using an IMMULITE 1000 Analyzer, with chemiluminescent immunometric assay, levels of interleukin-8 (IL-8) were measured in the pleural fluid of patients with UCPPE (n=30), and CPPE (n=30), and three classical parameters (pH, glucose, and LDH) in these two groups. Receiver-operating curves were to assess the sensitivity and specifity of interleukin-8 for differentiating between the two patient groups. IL-8 levels were statistically higher in the CPPE group. A positive significant correlation, was found between levels of IL-8 and and lactate dehydrogenase (LDH) (r=0.68, p<0.05). There was also a positive significant correlation between IL-8 and protein level in pleural effusion (r=0.306, r<0.01). There was a significant negative correlation between levels of IL-8 and pH (r=-0.83, p<0.05), and of IL-8 and glucose in pleural fluid (r=-0.61, p<0.05). A cut-off value of 1805.81 pg/ml, differentiated CPPE from UPPE with a sensitivity of 100% and a specifity of 98%. IL-8 may be used as an alternative marker for the complication of parapneumonic effusion.