Fully integrated lab-on-a-chip systems for applications such as DNA sequencing and pathogen detection will incorporate significant microfluidic components. These systems will necessarily require the flow of large molecules such as DNA, which give the bulk fluid viscoelastic behavior. Additionally, the contour lengths of these molecules L, will approach those of the fluid channel h (L/h/spl sim/0.25) presenting a unique flow situation that is not well understood. Flow visualization of dilute and semi-dilute lambda-DNA solution flows through a gradual contraction device is used to characterize the viscoelastic behavior. Deviations from Newtonian flow fields brought about by the viscoelastic fluid rheology and concentration effects are assessed.