The dissolution behavior of polystyrene (PS) in biodiesel was studied by developing a novel high throughput approach based on Fourier-transform infrared (FTIR) microscopy. A multiwell device for high throughput dissolution testing was fabricated using a photolithographic rapid prototyping method. The dissolution of PS films in each well was tracked by following the characteristic IR band of PS and the effect of PS molecular weight and temperature on the dissolution rate was simultaneously investigated. The results were validated with conventional gravimetric methods. The high throughput method can be extended to evaluate the dissolution profiles of a large number of samples, or to simultaneously investigate the effect of variables such as polydispersity, crystallinity, and mixed solvents.