Spectroscopic Evidence for Quasar Microlensing

We report on a number of ongoing experiments to obtain spectrophotometric data of lensed quasars. We find that spectral differences are a widespread phenomenon, suggesting that microlensing is very common. We discuss some aspects of how to distinguish microlensing from other sources of spectral differences. Extinction by intervening dust can have similar broad band signatures, but can be distinguished or even separated from microlensing using spectrophotometry. We present recent results on extinction and microlensing in a z=0.93 lensing galaxy. We also present a case study of the issue of discrepant flux ratios in a quadruple QSO, where we find that microlensing probably plays a role. We finally discuss the aspect of microlensing-induced emission line profile variations.