CheXagent is a chest X-ray interpretation tool based on visual language foundation models. It leverages clinical large language models to parse radiology reports, visual encoders to represent X-ray images, and designs a network to bridge the visual and language modalities. Additionally, CheXagent introduces CheXbench, a new benchmark designed to systematically evaluate the performance of visual language foundation models on eight clinically relevant chest X-ray interpretation tasks. Through extensive quantitative evaluation and qualitative review by five expert radiologists, CheXagent outperforms previously developed general-purpose and medical domain foundation models on CheXbench tasks.