Title: CroMA: Cross-Modality Adaptation for Monocular BEV Perception. Abstract: Incorporating multiple sensor modalities, and closing the domain gaps between training and deployment are two challenging yet critical topics for self-driving. Existing adaption works only focus on visual-level domain gaps, overlooking the sensor-type gaps which exist in reality. A model trained with a collection of sensor modalities may need to run on another setting with less types of sensors available.  In this work, we propose a Cross-Modality Adaptation (CroMA) framework to facilitate the learning of a more robust monocular BEV perception model, which transfer the point clouds knowledge from LiDAR sensor during training phase to the camera-only testing scenario. The absence of LiDAR during testing negates the usage of it as model input. Hence, our key idea lies in the design of a LiDAR-teacher and Camera-student knowledge distillation model, as well as a multi-level adversarial learning mechanism, which adapt and align the features learned from different sensors and domains. This work results in the first open analysis of cross-domain perception and cross-sensor adaptation model for monocular 3D tasks in the wild. We benchmark our approach on large-scale datasets under various domain shifts and show state-of-the-art results against various baselines.