AbstractA simplified method for extraction of β‐hydroxybutyric acid from whole egg prepared from incubator reject eggs is described. It is concluded that the presence of 15.95 ± 8.54 mg of β‐hydroxybutyric acid per 100 g of liquid whole egg would strongly indicate that the egg had been prepared from incubator reject eggs. There is no obvious correlation between the numbers and types of bacteria present and the amounts of β‐hydroxybutyric acid found in incubator reject eggs. The relative merits of a test for the presence of incubator reject egg in egg products based on the estimation of β‐hydroxybutyric acid as opposed to alternative proposed tests, described in the literature, are reviewed.