Renal cell carcinomas (RCC) are a heterogeneous group of cancers that often include angiogenesis as a key clinical and pathological hallmark. As the transcription factor nuclear factor kappa B (NF-kappaB) has been identified as a key promoter of angiogenesis, NF-kappaB inhibitors could serve as potential anti-angiogenic agents. In this study, we tested the anti-angiogenic properties of pyrrolidine dithiocarbamate (PDTC), a NF-kappaB inhibitor, using established in vitro and ex vivo assays in human umbilical vein endothelial cells (HUVEC) and human metastatic RCC cell lines (ACHN and SN12K1). In vitro, PDTC inhibited proliferation, capillary tube formation, invasion and trans-differentiation of HUVEC. Ex vivo, PDTC blocked vessel sprouting from aortic explants and disrupted the integrity of pre-formed vessels. PDTC also inhibited the adhesion of HUVEC and RCC cells to substratum and inhibited their invasion. PDTC inhibited RCC-induced proliferation of HUVEC. Protein microarray demonstrated heterogenic actions in each cell line: in HUVEC, epidermal growth factor was significantly decreased; in ACHN, basic fibroblast growth factor, growth related oncogene, interleukin-6, RANTES and monocyte chemoattractant protein-1 (MCP-1) were significantly decreased; and in SN12K1, MCP-1 was upregulated. PDTC increased the expression of the pro-angiogenic protein interleukin-8 in both RCC cell lines. Expression of vascular endothelial growth factor (VEGF) was not significantly altered, and exogenous VEGF had a neutral effect on in vitro angiogenesis of HUVEC. Collectively, these data suggest that PDTC has some anti-angiogenic properties, which may limit development and progression of RCC.