The present invention provides a minimally-invasive portal system for performing lumbar decompression, instrumented fusion/stabilization, and the like. The minimally-invasive portal system utilizes an access tube having an adjustable cross-sectional area and one or more retractor devices each having a first portion and a second portion aligned at a predetermined angle relative to the first portion, wherein the first portion of each of the one or more retractor devices is disposed substantially concentrically with the access tube, and wherein the second portion of each of the one or more retractor devices protrudes substantially beyond a bottom portion of the access tube. The minimally-invasive portal system also utilizes a plurality of adjustment mechanisms for selectively adjusting the cross-sectional area of the access tube and one or more retaining clips for securing the one or more retractor devices to the access tube in a fixed position.