The objective of the study was to construct a short screening scale for posttraumatic stress disorder (PTSD). We used data from our previous study on PTSD among flood victims in 1998 and 1999 in Hunan, China, which was a representative population sample of 27,267 subjects from 16 to 94 years old. Multistage sampling was used to select the subjects from the flood areas and PTSD was ascertained with the Diagnostic and Statistical Manual of Mental Disorders: 4th Edition (DSM-IV). We randomly assigned 80% (n=21,762) of study subjects to construct the screening scale (construct model) and the remaining 20% (n=5505) to test the model. Logistic regression analysis and receiver operating characteristic analysis were used to select a subset of items (symptoms) from the full scale that would effectively predict PTSD. A seven-symptom screening scale for PTSD was selected. A score of 3 or more on this scale was used to define positive cases of PTSD, with a sensitivity of 87.9%, specificity of 97.9%, positive predictive value of 81.3%, and negative predictive value of 98.7%. The short screening scale developed in this study is highly valid, reliable, and predictable. It is an efficient tool to screen PTSD in epidemiological and clinical studies.