This issue of the IEEE Transactions on Nuclear Science (TNS) is devoted to the 21st IEEE-NPSS Real Time Conference (RT2018) on Computing Applications in Nuclear and Plasma Sciences held in Williamsburg, VA, USA, in June 2018. A total of 98 papers presented at the conference have been submitted for possible publication in TNS. The conference accepted 54 papers as oral and 149 as poster presentations in 13 tracks. [ABSTRACT FROM AUTHOR]