Tests for the detection of pregnancy early after insemination have not yet reached their full potential. Currently, the milk progesterone assay provides the earliest possible test, at an interval of one oestrous cycle after insemination, i.e. 17, 21 and 21 days in sheep, goats and cows respectively. This assay is pregnancy non-specific and rate of detection of pregnant animals is acceptable but less than desirable. Detection of activity of early pregnancy factor may develop into an excellent early test for many species, but the rosette inhibition test which is currently required has limited development and use. Pregnancy-specific protein B has been developed as a radioimmunoassay and is reliable under laboratory situations for ruminants. It can be used after 24 days of gestation in the cow. Application to field testing awaits development. Other pregnancy-associated or specific substances which are found in maternal body fluids might develop as pregnancy markers. Ultrasonic devices might provide very early detection in cattle but the expense of a test will limit application. All tests for pregnancy early after insemination have an inherent inaccuracy. Presence of an embryo at the time the test is applied will not assure pregnancy at the time of a confirmatory test, such as birth of live young or rectal examination in cows after 35 days of gestation. Therefore, no matter how early the test, a follow-up examination might be desirable in intensively managed herds or flocks. The animal industry is on the verge of new biotechnological approaches to reproductive management. The potential seems as great as the imagination.