Technical Abstract: The degradation of high molar mass polymers during size-exclusion chromatography (SEC) analysis has been a topic of interest for several decades. Should a polymer degrade during analysis, the accuracy of the molar mass (M) and architectural information obtained will be compromised. To this effect, a number of studies have provided extensive qualitative circumstantial evidence of the degradation of ultra-high molar mass polymers in SEC columns. The evidence generally given is a change in the elution profile of the analyte toward larger elution volumes as a function of increasing flow rate, elution volume in SEC being inversely proportional to analyte size in solution. Not only is very little understood about the types of flow fields involved in the degradation, but there is even doubt about whether degradation is even occurring. In many cases, the latter might instead be an unrecognized manifestation of slalom chromatography occurring within the SEC column. Here, using SEC coupled to both static multi-angle light scattering and differential refractometry detectors, we show unambiguous evidence of the degradation of the ultra-high-M polysaccharide alternan.