A number of sub-topic areas within public health featured no reviews or a very small number of reviews including those within the main topic areas for women's health (sub-topics include female genital mutilation, hormone replacement therapy, and infertility as examples); communicable disease/infection (sub-topics include food-borne diseases, hantavirus, and Norwalk, among others); food safety and inspection (sub-topics include botulism, food processing and inspection, and Hepatitis A as examples); dental health (sub-topic: dental implants); environmental health (sub-topics include asbestos, carbon monoxide poisoning, environmental epidemiology, extreme temperature, swimming pools, and flood, as examples). In these areas, review literature is needed to add to the existing body of literature from which decision makers can draw. In topic areas lacking in review literature, realist reviews, which provide explanatory analyses [23] , are a relatively new type of review that may provide further insight into the topic area. While these areas show the deficits in review literature, in 25 other sub-topic areas there was a wealth of systematic review literature of moderate or strong quality, including but not limited to, alcohol abuse/use, smoking cessation, women's health, cancer, cardiovascular disease, lifestyle behaviours, disease transmission, depression, diet, healthy weight, exercise, and HIV. In these areas offering many reviews, most had 15 or more which were of strong methodological quality. While review groups can identify and fill gaps in areas where evidence is lacking, there is also an opportunity to produce higher level syntheses where good-quality review evidence is available. Based on this analysis of the published, public health review literature catalogued in http://www.health-evidence.ca, all of the topic areas having many available reviews were also preferred areas of interest for users of the site. It is unclear how the availability of evidence is linked to interest in a topic, but it may be that demand can generate reviews in a particular topic area and that the public spurs research to fill gaps [24] . Alternately, preference for a topic may be a reflection of there being available evidence that drives interest in the topic and web site updates regarding that topic. Interestingly, the 15 priority topic areas indicated by a 2005 Cochrane global priority setting exercise [24] still closely match the top 10 topic areas of interest indicated by health-evidence.ca users and visitors.