A catheter system comprising: a catheter having an elongate flexible shaft, the shaft having an outer surface defining an outer transverse cross-sectional dimension; and a handle having a connector for connecting the catheter to the handle, the connector being generally tubular having a sidewall, an open front end, an open rear end and a channel extending longitudinally within the connector from the front end to the rear end thereof for receiving and retaining the catheter shaft in the connector, the connector sidewall having an outer surface and at least one projection extending transversely outward from the outer surface of the connector sidewall, wherein, over a first segment of the connector channel, an inner surface of the sidewall is tapered such that an inner transverse cross-sectional dimension of the connector channel increases as the connector channel extends towards the front end to provide a clearance between the catheter shaft and the connector; and a flex relief member is retained on the handle, the flex relief member being generally tubular and having a sidewall, an open front end, an open rear end and a channel extending longitudinally from the front end to the rear end of the flex relief member and being sized in transverse cross-section along its length to permit the throughpassage of the catheter shaft, said channel of the flex relief member including a housing segment extending longitudinally forward from the rear end of the flex relief member and configured for receiving at least a portion of the connector, front end first, into the channel of the flex relief member, the flex relief member further having at least one longitudinally extending groove open to the channel within the housing segment of the flex relief member and corresponding to the at least one projection of the connector to receive the at least one projection of the connector into said at least one groove to thereby inhibit rotation of the connector relative to the flex relief member following insertion of the connector into the flex relief member. a catheter having an elongate flexible shaft, the shaft having an outer surface defining an outer transverse cross-sectional dimension; and a handle having a connector for connecting the catheter to the handle, the connector being generally tubular having a sidewall, an open front end, an open rear end and a channel extending longitudinally within the connector from the front end to the rear end thereof for receiving and retaining the catheter shaft in the connector, the connector sidewall having an outer surface and at least one projection extending transversely outward from the outer surface of the connector sidewall, wherein, over a first segment of the connector channel, an inner surface of the sidewall is tapered such that an inner transverse cross-sectional dimension of the connector channel increases as the connector channel extends towards the front end to provide a clearance between the catheter shaft and the connector; and a flex relief member is retained on the handle, the flex relief member being generally tubular and having a sidewall, an open front end, an open rear end and a channel extending longitudinally from the front end to the rear end of the flex relief member and being sized in transverse cross-section along its length to permit the throughpassage of the catheter shaft, said channel of the flex relief member including a housing segment extending longitudinally forward from the rear end of the flex relief member and configured for receiving at least a portion of the connector, front end first, into the channel of the flex relief member, the flex relief member further having at least one longitudinally extending groove open to the channel within the housing segment of the flex relief member and corresponding to the at least one projection of the connector to receive the at least one projection of the connector into said at least one groove to thereby inhibit rotation of the connector relative to the flex relief member following insertion of the connector into the flex relief member.