Apparatuses of the type broadly applicable to numerous medical applications in which it is desirable to insert one or more steerable or non-steerable catheters or similar devices into a working channel of an associated device, such as an endoscope, catheter, etc., or passageway of a patient, are disclosed. The apparatuses may include catheters having a dedicated guide wire channel and one or more of the following: viewing capabilities, a working channel, and auxiliary channels, such as insufflation/irrigation channels. The catheters may include a guide wire channel that is configured to provide the catheter or other device with rapid exchange capabilities.