The Ryle Telescope (RT) has been designed to image the cosmic microwav
e background radiation (CMBR) with low systematic error, and in partic
ular to study the Sunyaev-Zel'dovich (S-Z) effect. I present RT maps o
f the S-Z effect in four galaxy clusters: 0016 + 16, Abell 733, Abell
1722 and Abell 2218. Decrements in the CMBR are detected at levels of
4-5 sigma in all four.