The serum from virtually all people exposed to Toxoplasma gondii contains a high titer of antibodies against a major antigen called P30. It has been suggested that p30 antigen can be used as a good diagnostic tool during T. gondii infection. Polymerase chain reaction (PCR) is the most widely used method for amplifying a known of nucleic acid fragment. We have cloned the P30 gene by PCR using oligonucleotide primers, based on the reported sequence of the T. gondii p30 gene, and introduced it into the pEV142 expression vector. Work is in progress to explore the use of pEV142 expression vector in transgenic mice in order to study the immunological role of p30 antigen during T. gondii infection.