Abstract Tumor immunotherapy relies on improved anti-tumor activity of the immune cells. Efficacious immunotherapy often correlates with increased CD8+ T cell infiltration within the tumor, subsequently resulting into reduction in tumor growth and morphological remodeling. However, pan- melanoma visualization of immune cell infiltration and associated macro-scale alterations in tumor morphology and vasculature remains extremely challenging. This is largely owing to the dense pigmentation, thick extracellular matrix deposition and friable texture of the tumor, rendering it optically inaccessible using the routine histology and organ clarification techniques. Here, we describe a rapid and inexpensive optical clarification technique that enables examination of immune infiltration as well as vascular changes, both at tissue level as well as single cell-resolution within an intact tumor. The aforementioned technique, termed Tumor-optimized three-dimensional imaging of solvent cleared organs (T-DISCO), combines in vivo fluorescent labeling of the endogenous immune cells with organic solvents-based tissue clarification and eventual image acquisition using a standard confocal microscope. This technique when applied to the B16F10 melanoma model undergoing a multi-component immunotherapy, revealed changes within the tumor microenvironment, including vascular normalization and intra-tumoral trafficking of the T cells. Thus, T-DISCO represents a powerful tool to examine and investigate immune cell behavior deep within the intact tumor. Citation Format: Sudha Kumari, Kelly Moynihan, Darrell J. Irvine. High-resolution visualization of immune response across the intact melanoma tumor. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr A25.