The Lotto jackpot will break the €6m mark tonight, only the third time this year.
Punters are being urged to buy their tickets early to beat the queues and be in with a chance of snapping up the big win.
A spokeswoman for the National Lottery said business was expected to be brisk at outlets throughout the day.
“Play levels are expected to be very high in Lotto agent outlets. So get your ticket now and be in with a chance to be a big winner with Lotto, the only game in town this week,” she said.
In January €8.6m was won up by a lucky player in Kilkenny, while €6.7m and €7.3m were won in Dublin in March and May.