Purpose: Almost all patients with suspected appendicitis have plain abdominal radiographies (PAR) at the emergency departments. The aims of this study are to evaluate the ability of PAR to diagnose suspected acute appendicitis in patients and to predict length of hospital stay (LOS). Methods: Three blinded radiologists retrospectively and separately reviewed the preoperative PARs of all patients with suspected appendicitis, who underwent surgery in our hospital for 1 year period based on 8 radiologic criteria. The patients were divided into 3 groups [acute appendicitis (group 1), perforated appendicitis (group 2), and negative appendectomy (group 3)] according to their perioperative and pathological findings. The relationship between the presence/absence of the PAR findings and the diagnosis and LOS were analyzed. Results: The study consisted of 162 patients (103 men, 63.6%). There were 96 (60.5%), 45 (27.8%), and 19 (11.7%) patients in groups 1, 2, and 3, respectively. Although there were more men in the study overall (p < 0.001), there were more women in groups 2 and 3 than group 1 (p=0.004, p < 0.001, respectively). Group 2 had the longest LOS, and Group 3 had the shortest LOS (p < 0.001). The generalized air-fluid level was more commonly observed in group 2 patients (7 of 45) than in group 1 patients (2 of 98) (p<0.05). The LOS was longer in group 3 when the sentinel loop was present on the PAR (n=3) (p = 0.017), and in group 2 when the colon cutoff sign was positive (n = 3) on the PAR (p = 0.006). Conclusions: Our results suggest that PAR is rarely beneficial in the diagnosis of acute appendicitis and in the prediction of LOS. The PAR may not be a necessity for all patients with suspected acute appendicitis. 2003 by the Association of Program Directors in Surgery).