There were 166 newly diagnosed cases of HIV for gay and bisexual men in Ireland in 2012.
The figures released by the HSE’s Health Protection Surveillance Centre are the highest diagnosis rates recorded to date.
HIV diagnosis rates among gay and bisexual men have increased by 160% between 2005 and 2012, and now represent just under half, or 48%, of all new HIV diagnoses.
Tiernan Brady, Director of Gay HIV Strategies with GLEN, said the age profile of those gay and bisexual men diagnosed with HIV is also coming down.
Mr Brady said: "It is that age group between 25 and 34, and we've seen the age gradually decline over the last five years.
"The average age this year is 32, that has gone down from 38, so that means there is a new generation of younger gay and bisexual men who weren't around in the 80s and 90s when there would have been significant public awareness campaigns about HIV and Aids."