Almost a third of people living with HIV are unaware they carry the infection, new research has revealed.
Campaigners warned that people are still involved risk-taking behaviour because they do not think they will get HIV.
Barriers to testing for the infection have also led to late detection and have prevented people from benefiting from early treatment, it was claimed.
Dr Jack Lambert, infectious disease consultant at the Mater Hospital, warned a late diagnosis could lead to the rapid onset of Aids.
Dr Lambert said: "We have to continue challenging the stigma that still surrounds HIV in Ireland in order to effect change.
"The public needs to know that by avoiding early HIV testing, you put yourself at risk of rapid disease progression -- possibly leading to Aids."
A total 6,287 people in Ireland have been diagnosed with HIV since the early 1980s.
While the overall diagnosis rate decreased by 3pc in 2011, more than half of the 320 people who tested positive presented late with the illness.
And 27pc of the 85 women diagnosed were pregnant.
The highest proportion of new cases was among men who have sex with men (42.5pc), and 5pc were injecting drug users.
The figures were released ahead of Irish Aids Day -- on Friday June 15. -- when a Don't Guess, Get Tested campaign will be launched by Open Heart House, the Sexual Health Centre, Aids West, Dublin Aids Alliance and the Red Ribbon Project.