As an expert in neither Antarctic politics nor international law, I concede to being somewhat impressionable in my uptake of information on these subjects. It was recently conveyed to me that the success of the Antarctic Treaty System (ATS) was due in a large part to its flexibility. This assertion seemed plausible, the Treaty has endured and accommodated significant international changes over last 50 years, and through its instruments and measures has successfully maintained the Antarctic as a place for peace and science, the respective objects of Article I and II of the Antarctic Treaty. If flexibility is a quality which has afforded such success then in relation to the Treaty it is considered here a topic worthy of further exploration. The first part of this review provides a scan of the Antarctic literature in an effort to understand the origins of ATSs reputation for the flexibility of the system as a whole. In doing so, this review identifies a shift over time in the identification of flexibility as a positive attribute of the system, to one having increasingly problematic consequences. Within the Annexes and Articles of Treaty instruments themselves a second use of flexibility as a concept is also detected, particular attention is paid to Article IV of the Treaty which is central to the issue of flexibility for the system as a whole. Article IV has also been subject to diverse and evolving opinion regarding its effect on the overall ability of the system to accommodate change. Some see it as a universally accommodating mechanism which will take the Treaty forward (Beck, 2009; Heap, 1983; Joyner, 1999; Watts, 1986), whilst others see it as limiting and cause for the ATS to have stalled in recent years (Grob, 2007; Hemmings, 2007; Marcoux, 1970). The second and third parts of the paper review briefly explore an observe shift from the use of flexibility to ambiguity in the language used to describe the ATS. At this point, reference material is extended outside the literature of Antarctica to broader sources which consider the use of ambiguity as a constructive mechanism. As a conclusion some questions are proposed regarding the idiosyncrasies of ambiguity in the context of the ATS.