This review summarizes existing knowledge on the development and use of the polymerase chain reaction for the detection of DNA from Neospora and Toxoplasma. Several strategies which utilise the polymerase chain reaction for the diagnosis of toxoplasmosis in humans and livestock have been described and they principally target the B1 repetitive sequence, the P30 gene or ribosomal DNA. Experience has shown that the polymerase chain reaction has proven insufficiently robust to serve as a diagnostic test alone although when used in conjunction with other diagnostic techniques it does prove to be a useful aid. The marketing of a commercial polymerase chain reaction kit may well solve some of the inadequacies seen using "home made" polymerase chain reaction technology which are commonly used in diagnostic laboratories around the world. Recent progress on the development of polymerase chain reaction diagnostics for Neospora has been rapid and is discussed in detail.