AbstractThis review followed from experiments suggesting that some fungi do not require calcium. It was found that many studies of a calcium requirement in microorganisms had assumed specificity for chelation agents such as EGTA and A23187, which the reagents did not possess. Early studies still cited today often preceded the recognition that microorganisms required manganese and zinc. As a result of both of these misunderstandings, there was rarely any attempt to replace calcium by other important trace elements. In some studies that seem to have been overlooked, the apparent requirement for calcium depended on the growth conditions used.Escherichia coli, Neurospora crassa, andSaccharomyces cerevisiaewere then selected for detailed consideration and it is concluded that further experiments are needed before the involvement of calcium is proved.