Objective. To determine the diagnostic value of sequential white blood cell count (WBC), tumor necrosis factor-alpha (TNF-alpha) and interleukin- 6 (IL-6) in patients with abdominal pain. Material and methods. Tests were determined at hospital admission and 6 h later in 105 children. Patients who were nonoperatively followed and had a normal histopathology were classified as the non-appendicitis (NA) group. Patients with symptoms consistent with appendicitis were classified as the appendicitis group ( A). Data were analyzed as positive/negative predictive value, sensitivity, specificity and accuracy rate (AR). The global power of the variables in discriminating the patients between the two groups and advanced/simple appendicitis was assessed from the area under the receiver operating characteristic (ROC). Results. Initial measurements showed WBC to be a valuable diagnostic tool in acute appendicitis (AR = 74%), whereas IL-6 and TNF-alpha were found not to be valuable. The second measurements revealed higher values, and IL-6 reached its highest AR (89%). When initial values were evaluated in combination, the highest AR of 73% was observed with TNF-alpha + WBC. The highest AR (90%) was seen with IL-6 + TNF-alpha in the second measurements. ROC analysis showed WBC to be the most valuable parameter of the three. The area under the curve (AUC) was 0.750 for the initial measurement and 0.779 for the repeat measurement of WBC (p = 0.001). The most useful diagnostic parameter in discriminating between the simple and the advanced cases was IL-6 as assessed with the ROC curve (p < 0.01). Conclusions. WBC elevation in patients with suspected acute appendicitis is an important parameter supporting the diagnosis at initial admission, whereas IL-6 is a more valuable tool in diagnosing advanced appendicitis.