In induction machines, besides fundamental losses, the stray losses represent a significant part of the total losses. They highly influence dimensions of electrical machines i.e. material costs for their production as well as energy consumption. Induction machines spend a large part of working time at no-load. Since it is also the first step to determine their losses, induction machines with squirrel-cage at no-load are analysed in this work. This work deals with the reasons for appearance of stray losses in induction machines, considering especially slotting on the stator and the rotor side of the air gap, along with the appearance of the cross-bar currents of the non-isolated squirrel-cage. The analytical approach gives a simple, but for the engineering practice more suitable and precise, calculation of the stray losses of the induction machines with squirrel-cage at no-load. Also, the comparison of that analytical calculation with the measurements of losses at no-load is given for two squirrel-cage induction motors. The thesis presents an analysis of the rotor stray losses depending on the bar-to-iron contact resistance for different skews of the cage and the number of rotor slots, which represents a great advantage of the analytical approach to the calculation of stray losses.