The shear layer and the near wake region of right trapezoidal prisms with varying streamwise aspect ratios in a uniform flow were investigated using particle image velocimetry. The tested streamwise aspect ratios (AR) based on the height and upper surface were 1 and 4. The Reynolds number based on the prism height and the freestream velocity was 14700. The effects of aspect ratio on the mean flow, Reynolds stresses and third-order moments were investigated, and the results were compared with a square prism. The results show that mean flow separation at the leading edge is not affected by the different geometries and the streamwise aspect ratios. However, the mean recirculation bubbles over the prism and in the wake region show significant differences. Mean flow reattaches over the prism in the AR4 case, but there is no reattachment in the AR1. One-dimensional profiles are used to quantitatively assess the differences in the flow characteristics. It is observed that the magnitudes of Reynolds stresses in the near wake region are an order higher in the AR1 case than in the AR4 case.