A catheter having an internal advancing mechanism that can advance stiffening wires or other devices, has a catheter with a catheter body, a tip section distal the catheter body, a device extending through at least the catheter body, and a control handle proximal the catheter body, where the control handle has an advancing mechanism with a threaded member, an adjustment member, and a guided member to which the device is connected, and the advancing mechanism is configured to advance and retract the device along the catheter body as controlled by a user. Each of the threaded member and the adjustment member has a generally cylindrical configuration. The threaded member has an outer surface configured with a helical guide channel. The adjustment member is configured to guide the guided member to move within the helical guide channel to advance and retract the device. The adjustment member can be rotatable over the threaded member by the user to control advancement and retraction of the device. The device may be a stiffener wire, a needle or any other device suitable for advancement and retraction in a catheter.