Foodborne illnesses are an important public health problem in the United States in terms of both the burden of illness and cost to the health care system. Strengthening foodborne illness surveillance helps address the growing issues of food safety in the United States. Very little is known about the use of consumer complaint surveillance systems for foodborne illness. This study evaluates the use of these surveillance systems by local health departments (LHDs) in the United States and their practices and policies for investigating complaints. Data for this study were collected through two Web-based surveys based on a representative sample of LHDs in the United States; 81% of LHDs use complaint-based surveillance. Of those that did not have a complaint system, 64% reported that the state health department or another agency ran their complaint system. Health departments collect a wide variety of information from callers through their complaint systems, including food intake history. Most of the LHDs, however, do not store the information in an electronic database. Outbreak rates and complaint rates were found to be positively correlated, with a Pearson's correlation coefficient of 0.38. Complaints were the most common outbreak detection mechanism reported by respondents, with a median of 69% of outbreaks during the previous year found through complaints. Complaint systems are commonly used in the United States. Increasing the rate at which illnesses are reported by the public and improving investigation practices could help increase the number of outbreaks detected through complaint surveillance.