Pooled fecal culture is being considered as an alternative to ELISA testing for determination of herd M. paratuberculosis status and identification of groups of animals warranting individual fecal culture. In the USA, fecal culture is the only officially-recognized test yet it is cost-prohibitive to do individual fecal cultures for all cows in large dairy herds. In an experimental study, the sensitivity of pooled fecal culture (pools of size 5 and 10) ranged from about 30% to 100% and was strongly dependent on pool size and whether cows were shedding many (heavy shedders) or few (light shedders) M. paratuberculosis. The present study was done to evaluate the accuracy of pooled fecal culture (pools of size 10) compared with ELISA testing and individual fecal culture under field conditions. We studied 29 dairy herds that were clients of a single dairy practice in the Central Valley of California. Herds ranged in size from 300 to 1500 cows and all herds except one had not been previously tested for M. paratuberculosis. In each herd, sixty lactation-2 or older cows were randomly selected and blood and feces were collected for ELISA testing and culture, respectively. Feces was frozen at -70 until pooled for fecal culture. Pooled fecal cultures were done by 2 methods (TREK and traditional culture methods). ELISA data indicated that at least 27 of 29 herds were likely infected. Culture results are pending.