A downhole apparatus comprises a body (14), extendable members (12) mounted on the body (14) and being movable between retracted and extended configurations, and a remotely operable retaining arrangement for maintaining the extendable members in the retracted configuration. The extendable members (12) may be cutters, such that the apparatus may be a cutting apparatus, such as a reamer. An operator may control the apparatus to retain the cutting members (12) in the retracted configuration, or prevent the extension of the cutting members (12).