Figures released by the Health Service Executive show that there were 166 newly diagnosed cases of HIV among gay and bisexual men in Ireland in 2012.
The figures are the highest diagnosis rates recorded to date.
HIV amongst gay and bisexual men increased by 160% between 2005 and 2012 and now represents just under half of all new HIV diagnoses.
The figures also show the average age of HIV diagnosis has fallen to 32 years of age in 2012.
Tiernan Brady of the Gay and Lesbian Equality Network told RTÉ News that the figures show that gay and bisexual men are the group most likely to acquire HIV in Ireland.
"It is clear from the figures that HIV is a critical issue of growing concern. The trend is very worrying," he said.