The focus of this training course will be on understanding and measuring ac losses in superconductor wires and tapes. Due to the complex manner of this electrical engineering topic, intense theoretical background training will be offered. The course will discuss different strategies to reduce ac losses, introduce ac loss simulation tools and examine a variety of ac loss measurement techniques. The course of AC loss technique will, in its first part, comprise the practical laboratory training in standard methods (determination of transport and magnetization loss of a standard tape), with particular emphasis on the reliable detection of correct loss signals at levels starting from 10-8 V, the compensation of the inductive component of measured voltage and the phase sensitive detection of the useful signal component. Young researchers will be trained to catch the loss signal from background noise, to recognize its typical shape and check its waveform with the help of harmonic analysis. In the second part of the course, one non-standard method will be selected according to the particular research interest of the trainee. The aim will be to let him acquire the experimental skills necessary to use a simple version of the experimental system in his laboratory and to carry out the experiments independently in the proper way. This training course is organized by Dr. Gömöry and will take place from April 7th to April 10th in Bratislava.