This article presents review and opinion about the use and abuse of journal impact factors for judging the importance and prestige of scientific journals in the field of forensic science and toxicology. The application of impact factors for evaluating the published work of individual scientists is also discussed. The impact factor of a particular journal is calculated by dividing the number of current year citations to a journal’s articles that were published in the previous 2 years by the total number of citable items (articles and reviews) published in the same 2-year period. Journal impact factors differ from discipline to discipline and range from 0 for a journal whose articles are not cited in the previous 2 years to 46 for a journal where the average recent article is cited 46 times per year. The impact factor reflects the citation rate of the average article in a journal and not a specific article. Many parameters influence the citation rate of a particular journal’s articles and, therefore, its impact factor. These include the visibility and size of the circulation of the journal including availability of electronic formats and options for on-line search and retrieval. Other things to consider are editorial standards especially rapid and effective peer-reviewing and a short time lag between acceptance and appearance in print. The number of self-citations and citation density (the ratio of references to articles) and also the inclusion of many review articles containing hundreds of references to recently published articles will boost the impact factor.