The International Conference on Formal Methods in Computer Aided Design (FMCAD), held at Austin, Texas, from October 3 to November 2 in 2018, is the eighteenth in a series of meetings on the theory and applications of rigorous formal techniques for the automated design of systems. The FMCAD conference covers formal aspects of specification, verification, synthesis, testing, and security, and is a leading forum for researchers and practitioners in academia and industry alike.This special issue of the journal on Formal Methods in System Design (FMSD) features extended and revised versions of select contributions from FMCAD 2018. Each contribution received at least two round of peer reviews by at least two experts. The issue contains the following contributions: