To estimate multipliers linking surveillance of salmonellosis, campylobacteriosis, and Shiga toxin-producing Escherichia coli (STEC) infections to community incidence, we used data from a gastroenteritis survey and other sources. Multipliers for severe (bloody stool/long duration) and milder cases were estimated from the component probabilities of doctor visit, stool test, sensitivity of laboratory test, and reporting to surveillance system. Pathogens were classified by the same severity criteria and appropriate multipliers applied. Precision of estimates was quantified by using simulation techniques to construct 95% credible intervals (CrIs). The multiplier for salmonellosis was estimated at 7 (95% CrI 4-16), for campylobacteriosis at 10 (95% CrI 7-22), and for STEC at 8 (95% CrI 3-75). Australian annual community incidence rates per 100,000 population were estimated as 262 (95% CrI 150-624), 1,184 (95% CrI 756-2,670), and 23 (95% CrI 13-54), respectively. Estimation of multipliers allows assessment of the true effects of these diseases and better understanding of public health surveillance.