Scientometrics of Horizontal Gene Transfer Research during 1991-2005 De-Cheng Yu1#, Wen-Ta Chiu2,3 and Yuh-Shan Ho1* 1Bibliometric Centre, Taipei Medical University - Wan-Fang Hospital 2Graduate Institute of Injury Prevention and Control, Taipei Medical University 3Department of Neurosurgery, Taipei Medical University Wan Fang Hospital Introduction Horizontal gene transfer or lateral gene transfer, is the collective name for processes that permit the exchange of DNA among organisms of different species. Traditional thought was that microorganisms evolved clonally, passing genes from mother to daughter cells with little or no exchange of DNA among diverse species. Recent studies of microbial genomes have shown that genomes contain genes that are closely related to a number of different prokaryotes, sometimes to phylogenetically very distantly related ones. The horizontal movement of gene play an important role in the evolution of microorganisms. Our purpose was to study the horizontal gene transfer research based on 1,172 documents published in Science Citation Index (SCI)-indexed periodicals between 1991 and 2005. These documents were analyzed and evaluated according to publication distribution and were used to determine the quantitative characteristics of horizontal gene transfer research. Methods Documents used in this study were based on the databases of the SCI which was accessed from the ISI Web of Science. Horizontal gene transfer was used as keywords to search titles, abstracts, and keywords. Table 1. Publication activity of top ten countries Results Table 2. Major characteristics of the research P: No. of articles PG: Total pages AU: No. of authors NR: Cited reference count SP: single country publications CP: international collaboration publications CPP: 3 year (including publish year) citation per publication Figure 1:Conmulative number of publication Conclusions Ten document types were found in the total of 1,172 documents published in 255 journals. USA has highest publication (38%) with 12 of citation per publications and followed distantly by United Kingdom. The G7 industrial countries (USA, Japan, Germany, UK, France, Italy, and Canada) represent a share of corresponding authors of 72% of world articles and 83% citations. Thirty-seven percent of all articles were published in journals which listed in the category of Microbiology. The most frequently used author keyword in articles was ‘horizontal gene transfer’ (47%), and followed by ‘evolution’ (7%), ‘phylogeny’ (5.9%), ‘gene transfer’ (4.8%), and ‘escherichia coli’ (3.7%). The most productive corresponding institute was the University of Wurzburg at Germany with 14 articles and 7.36 of citation per articles. 6.8% of all articles were published in Journal of Bacteriology with impact factor 4.146. There were 16% articles never be cited since it was published. 7.3% articles was cited once and 5.5% articles was cited 2 times.