Nearly one in two people who sought help from the country's sexual-assault treatment units last year had drunk at least the equivalent of two pints of beer.
Some had consumed as much as 15 units of alcohol - more than seven pints of beer or two bottles of wine.
The high levels of alcohol consumption are revealed in the annual reports of the units in Dublin, Cork, Galway, Mullingar, Letterkenny and Waterford.
Nearly one in five of those who sought help were unsure if a sexual assault had occurred.
The centres reported 712 attendances last year, including 45 men - an increase of 27 compared to 2015.
The average age of the alleged victims was 25 but they ranged from 13 to a woman of 80.
A total of 68.4pc reported the incident to the gardaí.
The majority of incidents happened between 9pm and 9am.
More than three-quarters reported a recent assault and, in the majority of cases, the alleged perpetrator acted alone.
The Cork centre reported that eight cases happened at a notable event, including UCC Rag Week, the June Bank Holiday, Leaving Cert results night, the Timoleague Festival and Fresher's Week. Half of the centre's clients were students.
In Donegal, the busiest months were May, June, July and August. A total of 84pc had drunk more than six units of alcohol, the equivalent of at least three pints.
October was the busiest month for the Galway unit and Sunday was the most frequently reported day for incidents.
The report said that 65pc of alleged victims had drunk more than four units of alcohol in the previous 12 hours.
One-third were concerned that drugs had been used to facilitate the assault.
Eleven cases involved teenage assailants, all of whom were male.
The Mullingar centre said that in 22pc of cases the assailant was a stranger. December was its busiest month.
The Dublin centre, at the Rotunda Hospital, had 289 attendances and January was its busiest month.
The youngest was 13 and the oldest 59.
Of the 52 people who were unsure if a assault had occurred, 43 had consumed alcohol and nine had taken drugs.
The Waterford centre said nearly three-quarters of its clients made a report to gardaí. August and October were its busiest months.
The Dublin Rape Crisis Centre has repeatedly warned of the risks of people letting their guard down as part of its 'stay safe' tips.
However, it has also pointed out that warning young women about the risks of being drunk is not tantamount to blaming them for any violence done to them.