Eliburn Support Services in Livingston hosted a celebration afternoon tea for their services users, staff and invited guests to mark the special milestone.
For the last 40 years, Eliburn Support Service have provided quality care and support to adults who have a learning disability, associated physical disabilities and who also have complex health care needs.
Over the years, hundreds of people have been supported by the dedicated staff at Eliburn Support Services to take part in meaningful activities, both in the service and within the local community.
Carol Brown, Interim Assistant Manager of Eliburn Support Services, said: "Huge thanks to everyone who came along to share our Ruby anniversary celebrations.
"It was amazing to see so many of the service users, past and present, their families and staff from over the years join us for the big day.
"Everyone enjoyed sharing some fun stories from across the last 40 years of the service, and sharing some of those memories from the past was a real highlight.
"A huge amount has changed since the service was opened in 1983, but what hasn't changed is the caring and compassionate ethos of Eliburn Support Service. We remain dedicated to supporting people of all abilities, to explore, learn, develop and excel.
"Thanks to everyone who has donated to us over the years, with those donations being used to benefit everyone who uses the service.
"Our service users, their families and staff also give a lot back to the local community and in the last year alone have volunteered with the foodbank, made donations to the Dogs Trust and Seagull Trust and raised an amazing £2,200 for Cash for Kids event."
Executive councillor for social work and health Anne McMillan said: "Many congratulations to everyone at Eliburn Support Services on their 40th anniversary.
"It's fantastic to see so many people come together to celebrate the positive impact the service continues to have on so many individuals and the local community."