Thousands of anti-abortion protesters thronged Parliament Hill and marched through the downtown on Thursday in what has become an annual rite.
It was the 14th year for the demonstration, which organizers call the "national march for life."
The crowd mustered on the broad lawn in front of the Peace Tower, listening to speeches, then moved off for a parade through city streets.
Some demonstrators waved placards urging the adoption of a new abortion law. Others carried religious icons and flags.
Some stood silently before gruesome photos of aborted fetuses.
The protest is held each May 12 to mark the 1969 passage of legislation that legalized abortion in Canada under certain conditions.
Those in attendance included high-school students, activists and senior clerics, including Terrence Prendergast, Roman Catholic archbishop of Ottawa.
But unlike past years, a sizable gathering of about 200 counter-protesters gathered near the anti-abortion group before they were escorted off the Hill by police following argumentative confrontations.
Although Prime Minister Stephen Harper's Conservatives won a majority government in last week's federal election, few of the anti-abortion protesters thought that will make a difference for their cause.
Mr. Harper was adamant during last month's election campaign that there will be no change in Canada's abortion law under his watch.
"As long as I am Prime Minister we are not opening the abortion debate," Mr. Harper said. "The government will not bring forward any such legislation and any such legislation that is brought forward will be defeated as long as I am prime minister."
Jen Bradley of Milton, Ont., a teacher who brought some of her teenage students to the capital for the march, wasn't investing much in Mr. Harper. She's betting on changing opinions through rallies like Thursday's.
"I do think that a march like this, a doubling of numbers and spreading the word, such as it is, is a step in the right direction," she said.
Father Tom Lynch, a Roman Catholic priest, was another who thought the Conservatives aren't going to help the cause.
"I think Stephen Harper has made it very clear that he and other political leaders don't want to re-open, as he puts it, the issue of abortion or other pro-life issues," Father Lynch said.
"But the reality is that with every new Parliament, with every new government, we have a moral duty and we have a civic right to be able to express our opinion to be able to achieve changes in public policy."
Pat O'Brien, a former Liberal MP who sat as an Independent after falling out with his party over abortion, said "the debate is on" and politicians will have to catch up with the public.
And Georges Buscemi, president of Campagne Quebec-Vie, said abortion services can be scaled back without a new law making the procedure illegal.
For instance, federal funding to family-planning organizations "can be diverted to other groups that are more open to life."
"There could be some behind-the-scenes work done," Mr. Buscemi said at news conference.
"Different things, subsidies to different organizations, policies on health, policies on education. There are a lot of things that can be done behind the scenes to prepare for the future."
March organizer Matthew Wojciechowski said there are now between 60 and 65 MPs out of 308 elected to Parliament who are in favour of new abortion laws.