The popular event is on at the recently-refurbished Paisley Town Hall until Saturday.
The beer festival is Scotland's largest and normally takes place in April but this year was put back while the refurbishment work was finished.
This week's festival has attracted more than 3000 people and will feature more than 160 different real ales from Scotland's small breweries.
Organisers, the Campaign for Real Ale, say it is a superb opportunity to taste beers from long-established breweries and new-start enterprises.
Derek Moore, beer festival organiser and founder of the Renfrew-shire Branch of the Campaign for Real Ale (CAMRA), said: "Each year we try to improve on the previous year's festival and this year's is no exception.
"The festival is the first big event at Paisley Town Hall since its refurbishment during the summer and we look forward to making this a successful event at this revitalised town hall."
For this year, the English bar will be located in the North Minor Hall and will feature beers from the Yorkshire region.
The Foreign Bier bar will boast draught and bottled biers from Belgium, Netherlands, Germany and many eastern European countries.
Admission to the 26th Paisley Real Ale Festival at Paisley Town Hall is £5.
The Caledonian Brewery Deuchars IPA Pipe Band will be playing around and inside Paisley Town Hall on Saturday.
For more information, visit www.paisleybeer festival.org.uk