A mutant allele of the β-chemokine receptor gene CCR5 bearing a 32-basepair (bp) deletion (denoted Δccr5) which prevents cell invasion by the primary transmitting strain of HIV-1 has recently been characterized1–3. Homozygotes for the mutation are resistant to infection, even after repeated high-risk exposures1,4, but this resistance appears not to be total, as isolated cases of HIV-positive deletion homozygotes are now emerging⁵. The consequence of the heterozygous state is not clear, but it may delay the progression to AIDS in infected individuals^2,3,6,7. A gene frequency of approximately 10% was found for Δccr5 in populations of European descent, but no mutant alleles were reported in indigenous non-European populations. As the total number of non-European samples surveyed was small in comparison with the Europeans the global distribution of this mutation is far from clear. We have devised a rapid PCR assay for Δccr5 and used it to screen 3,342 individuals from a globally-distributed range of populations. We find that Δccr5 is not confined to people of European descent but is found at frequencies of 2–5% throughout Europe, the Middle East and the Indian subcontinent (Fig. 1). Isolated occurrences are seen elsewhere throughout the world, but these most likely represent recent European gene flow into the indigenous populations. The inter-population differences in Δccr5 frequency may influence the pattern of HIV transmission and so will need to be incorporated into future predictions of HIV levels.