This special issue of International Journal of Fuzzy Systems (IJFS) published the latest, innovative and outstanding research results at the 2016 International Conference on Fuzzy Theory and Its Applications (iFUZZY 2016) held in Taichung, Taiwan, over November 09–11, 2016. Papers submitted to the IJFS special issue were initially reviewed by the guest editor and accepted as the oral presentation.

In accordance with the strict paper review procedure of IJFS, we invited six IJFS associate editors, Prof. Shun-Feng Su (the current Editor-in-Chief of IJFS), Prof. Chin-Wang Tao, Prof. Ching-Chih Tsai, Prof. Jin-Tsong Jeng, Prof. Chia-Feng Juang, and Prof. Yo-Ping Huang as the reviewers of all the oral presentations in iFUZZY 2016. Totally nine papers were selected according to the review criterion on completeness and technical contributions and asked for quality improvements according to the reviewers’ comments. Throughout the elaborative revisions by the authors, these nine papers have finally been accepted for publication in the IJFS special issue on fuzzy theory and its applications.

As for the presented contents of these nine papers in the special issue, we make brief introductions to their contributions on fuzzy theory and its applications. These articles provide interesting and timely innovative results covering adaptive predictive PID control using fuzzy wavelet neural networks for nonlinear discrete-time time-delay systems, fuzzy control strategy for a hexapod robot walking on an incline, image guided fuzzy c-means for image segmentation, strategizing for better life development using OECD well-being indicators in a hybrid fuzzy MCDM model, fuzzy modeling method based on rectangular pyramid fuzzy system, nonlinear behavior in Romeo and Juliet’s love model influenced by external force with fuzzy membership function, fuzzy theory using in image contrast enhancement technology, adaptive impedance force controller design for robot manipulator including actuator dynamics, and system reliability analysis method based on fuzzy probability. These nine papers bring a rich collection of fuzzy theory and its applications to illustrate the main technical achievements of the 2016 IJFS special issue in iFUZZY 2016. Finally, I would like to acknowledge all the contributors to this special issue and encourage your kind paper submissions to the 2017 IJFS special issue in iFUZZY 2017.

Guest Editor, 2016 IJFS Special Issue on Fuzzy Theory and Its Applications.