VARI 2013 is the 4rd European Workshop on CMOS Variability. The increasing variability in CMOS transistor characteristics, as well as its sensitivity to environmental variations has become a major challenge to scaling and integration. This leads to major changes in the way that future integrated circuits and systems are designed. Strong links must be established between circuit design, system design and device technology. VARI meeting answers to the need to have an European event on variability in CMOS circuits and technologies, where industry and academia meet to discuss and investigate the CMOS process and environmental variability issues in methodologies and tools for the design of current and upcoming generations of integrated circuits and systems. The technical program will focus on performance and power consumption as well as architectural aspects like adaptability or resilience, with particular emphasis on modeling, design, characterization, analysis and optimization of variability. Digital, Analog, Mixed Signal and RF circuits are within VARI scope.