We have developed a sensitive and specific method to identify Trypanosoma brucei ssp. using PCR to amplify conserved expression-site-associated gene 6 and 7 DNA target sequences. Amplification of 10% of the DNA in a single trypanosome produced sufficient PCR product to be visible as a band in an agarose gel stained with ethidium bromide. We analysed 59 blood samples of serologically positive cases of sleeping sickness by PCR, and directed parasitological examination of tissue fluids. The PCR test detected 87% of the parasitologically positive cases, with a specificity of 97%. In 5 cases, the parasite was demonstrated by the PCR test 4-6 months prior to parasitological detection. This result shows the potential of the assay in early diagnosis of actual T. b. gambiense infections in apparently aparasitaemic sleeping sickness patients.