Ferry operator Caledonian MacBrayne has warned of high demand for spaces on its boats on and around the weekend of HebCelt in Stornoway.
The music event is taking place on 19 to 22 July.
CalMac said people taking vehicles across should already have booked and urged foot passengers to do the same.
The company said Sunday 23 July was expected to be one of the busiest days with revellers trying to leave Lewis.
Stornoway Port manager Iain Don MacIver said: "We strongly encourage those planning to journey to and from Stornoway for the weekend of HebCelt, including foot passengers, to book their ferry slots, as soon as possible.
"Sunday is a particularly busy day with festival goers making their way home and it will be essential to have a valid booking for vehicles and passengers that day."
The Waterboys, Imelda May, Lucy Spraggan, Skerryvore, Peatbog Faeries and Dougie MacLean are among this year's HebCelt acts.
People who are planning on using ferries to get to Lewis for the Hebridean Celtic Festival have been urged to book their travel now.