Their bright neon signs have become more common on Montreal's streets, and the services offered can go far beyond simple relief from aches and pains.
Some even brazenly declare "XXX massage" in the window.
But these days Montreal's illicit massage parlours, viewed as a haven for prostitution and even human trafficking, are coming under increased scrutiny.
Newly elected mayor Denis Coderre has made a crackdown on the parlours one of his first orders of business at city hall.
Coderre wants to introduce legislation against them that would include hefty fines.
The move isn't without detractors, however.
It's part of a larger debate about the sex trade that has made its way to the Supreme Court of Canada.
Landmark decision on prostitution laws
This Friday, Canada's top court will bring down a landmark decision on the legality of the country's anti-prostitution laws.
Prostitution isn't illegal in Canada, but many of the activities associated with prostitution are classified as criminal offences — including operating a brothel, living off the avails and soliciting.
The Supreme Court must decide whether to keep Canada's current prostitution laws, throw them out, or offer an alternative.
Depending on Friday's ruling, erotic massage parlours like the ones popping up all over Montreal could, conceivably, become licensed, regulated venues for the sex trade.
As it stands, the establishments often hold a permit as a legitimate therapeutic massage business, hiding their true purpose.
Cities crack down on illicit massage parlours
Montreal has an estimated 350 illicit massage parlours operating across the city and many more in its suburbs.
Other cities have already taken steps to crack down on them.
Toronto introduced a bylaw this year making a distinction between massage parlours and erotic ones, and limiting the number of licenses available for erotic ones.
'There are children who live around there.' - Anie Samson, borough mayor for Villeray–Saint-Michel–Parc-Extension
Police in Calgary, meanwhile, raided a massage parlour in late October. Authorities shut it down for allegedly serving as a front for prostitution.
These days much of the focus has been on Montreal, where erotic massage parlours continue to be a city-wide issue.
More than 70 per cent of Montreal prostitution now takes place in such venues, according to a new survey by CLES, a group that advocates against the sexual exploitation of women.
Anie Samson, the borough mayor overseeing the effort to curb erotic massage parlours, said she's hopeful the crackdown will help make city neighbourhoods safer for families.
She described a triplex in her neighbourhood where there are illicit massage parlours on two of the floors, with people coming and going at all hours. A family lives on the other.
"There's not even a sign. They do all the advertising online," said Samson, mayor of Villeray—Saint-Michel—Parc-Extension.
"There are children who live around there."