It's feared the NHS could be at risk of privatisation as a result of a controversial trade deal.
The Transatlantic Trade and Investment Partnership between the EU and USA could create competition between American private healthcare providers and the health service.
Critics say the deal could expose the government to lawsuits if it tried to take privitised services back into public ownership.
Marches will take place in Aberdeen, Edinburgh, Glasgow and St Andrews later.
David Babbs, executive director at 38 Degrees, said: “One of the most worrying things about this deal is that it’s being agreed behind closed doors - so 38 Degrees members are taking to the streets to force it into the spotlight.
“People in Scotland will be standing with thousands of people across the UK to say that we love our NHS too much to let it be sold off to the highest bidder.
“It’s time for MEPs to answer our concerns and explain exactly what they’re going to do to stop this.”
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