The number of HIV infections averted, over 5 years and 20 years, with $1 million to spend on prevention targeting was calculated. Over 5 years the number of HIV infections averted ranged across the 9 target population scenarios, from 164 in the high-risk steady state group to 0.4 in the very low-risk, steady state group. Over 20 years these figures were between three and nine times as high. If the reduction in the frequency of risk behaviour was 50% the number of infections averted in the high risk steady state, over 5 years,increased to 830. Over 20 years it rose to 3750. In the very low-risk steady state target group, the number of infections averted over 5 years was 2 and over 20 years it was 9. If prevention was half as expensive, then twice as many infections would have been averted. For prevention to avert as many infections in low-risk steady state groups, as in high-risk steady state,the cost of intervention would have had to fall to $5 per person. To be comparable with other low-risk groups the annual cost would have had to fall to $1.