Unmethylated CpG dinucleotides have been found to stimulate general immune responses in mammals. CpG motifs have further been shown to be potent adjuvants when used in conjunction with vaccines for viral and bacterial organisms. It was necessary to determine whether these CpG motifs will also enhance immune responses in parasitic diseases. We therefore decided to test the effect of CpG adjuventation on immunization with a temperature-sensitive mutant (ts4) strain of Toxoplasma gondii. Mice were divided into groups receiving either ts4 only, CpG only, ts4 with CpG, or untreated controls. Mice were challenged with a lethal dose of T. gondii (RH strain) tachyzoites 28 days after vaccination. There were significant differences observed between the ts4-only group and the other three groups with regards to antibody isotype and survival, with the former group surviving lethal challenge. CpG adjuventation appeared to not enhance survival.