The rapid increase of ketamine abuse worldwide has created a need for a fast and efficient screening procedure. Currently, there is no commercially available immunoassay. We developed a simple extraction and GC/MS screening procedure to screen out negative samples. Urine samples (1 mL) were spiked with ketamine-d4 as internal standard. After liquid-liquid extraction, samples were screened for ketamine (K) and its two metabolites, norketamine (NK) and dehydronorketamine (DHNK), with GC/MS without derivatization. The total analytical time is 5 min for each sample. The detection limit for K, NK and DHNK was 10 ng/mL, 10 ng/mL and 30 ,ng/mL, respectively. The within-run precision and accuracy for 80, 160, 400 ng/mL of K, NK and DHNK were all between -12.50% and 8.17%. We collected 163 urine samples from disco-dancing clubs in Taiwan. Samples were screened and confirmed with GC/MS. The total analytical time for GC-MS confirmation is 20 min per sample. The sensitivity is 98.9% and specificity is 100%. This ,screening method is rapid, sensitive and applicable to forensic and clinical toxicological analyses.