Random amplified polymorphic DNA (RAPD) analyses were performed with random primer H16 for the B biotype and two non-B populations of Bemisia tabaci collected from Zhejiang (China). The specific sequence fragments containing 446, 390 and 1317 nucleotides were amplified for the B biotype, ZHJ-1, ZHJ-2 populations, respectively. The three specific fragments were cloned and sequenced, and three pairs of SCAR primers were designed according to the sequences determined. With improvement of the conditions of the polymerase chain reaction (PCR), the specific fragments of B biotype, ZHJ-1 and ZHJ-2 populations, namely 439, 366 and 1238 nucleotides, respectively, were amplified with the sequence characterized amplified region (SCAR) primer of the corresponding population, while specific fragments of the other populations of B. tabaci or Trialeurodes vaporariorum could not be amplified.