A stent introducer apparatus comprising: a primary stent introducer including an elongate pusher member, an elongate inner introducer catheter slidably disposed about the pusher member, and a first prosthesis removably mounted within the inner introducer catheter, the first prosthesis being expandable from a compressed pre-deployment configuration to an expanded deployed configuration, the first prosthesis being confined in the compressed pre- deployment configuration when disposed within the inner introducer catheter, the first prosthesis being permitted to expand to the expanded deployed configuration when not disposed within the inner introducer catheter; and a secondary stent introducer including an elongate outer introducer catheter and a second prosthesis removably mounted within the outer introducer catheter, the second prosthesis being disposed distally of the primary stent introducer, the outer introducer catheter being slidably disposed about the primary stent introducer, the second prosthesis being expandable from a compressed pre-deployment configuration to an expanded deployed configuration, the second prosthesis being confined in the compressed pre-deployment configuration when disposed within the outer introducer catheter, the second prosthesis being permitted to expand to the expanded deployed configuration when not disposed within the outer introducer catheter; wherein the first prosthesis is deployed by retracting the inner introducer catheter proximally relative to the pusher member so as to expose the first prosthesis from a distal end of the inner introducer catheter, and wherein the second prosthesis is deployed by retracting the outer introducer catheter proximally relative to the primary stent introducer so as to expose the second prosthesis from a distal end of the outer introducer catheter; characterised in that the outer introducer catheter comprises a port through a side wall of the outer introducer catheter, the side port proximal to the second prosthesis and configured to allow passage of the primary stent introducer therethrough. a primary stent introducer including an elongate pusher member, an elongate inner introducer catheter slidably disposed about the pusher member, and a first prosthesis removably mounted within the inner introducer catheter, the first prosthesis being expandable from a compressed pre-deployment configuration to an expanded deployed configuration, the first prosthesis being confined in the compressed pre- deployment configuration when disposed within the inner introducer catheter, the first prosthesis being permitted to expand to the expanded deployed configuration when not disposed within the inner introducer catheter; and a secondary stent introducer including an elongate outer introducer catheter and a second prosthesis removably mounted within the outer introducer catheter, the second prosthesis being disposed distally of the primary stent introducer, the outer introducer catheter being slidably disposed about the primary stent introducer, the second prosthesis being expandable from a compressed pre-deployment configuration to an expanded deployed configuration, the second prosthesis being confined in the compressed pre-deployment configuration when disposed within the outer introducer catheter, the second prosthesis being permitted to expand to the expanded deployed configuration when not disposed within the outer introducer catheter; wherein the first prosthesis is deployed by retracting the inner introducer catheter proximally relative to the pusher member so as to expose the first prosthesis from a distal end of the inner introducer catheter, and wherein the second prosthesis is deployed by retracting the outer introducer catheter proximally relative to the primary stent introducer so as to expose the second prosthesis from a distal end of the outer introducer catheter; characterised in that the outer introducer catheter comprises a port through a side wall of the outer introducer catheter, the side port proximal to the second prosthesis and configured to allow passage of the primary stent introducer therethrough.