In 2018 the average pay for female workers were 89,3 percent of the average pay for the male workers in Sweden. There are explanations for some of these differences, such as age, level of education and former experiences. Regardless, there is an unexplained pay difference at 4,4 percent. Since 1995, there has only been one win out of eight cases for the plaintiff regarding pay discrimination from the Swedish labor court. The aim of this essay is to highlight the differences in pay between men and women in Sweden and to clarify what the principle of equal pay for male and female workers for equal work or work of equal value is. In order to achieve this, the treaties, directives and preliminary rulings from the EU are studied. The rulings from the Swedish Labor Court are then critically reviewed in relation to the principle of equal pay. The study shows that the principle of equal pay aims to eliminate all types of discrimination based on gender regarding pay. Furthermore, the study shows that the Swedish Labor Court addresses to the EU law in cases regarding pay discrimination. However, the court fails to use the principle of proportionality when deciding whether the difference in pay is objectively founded. Also, the court fails to determine whether it is part of or all of the pay difference that is factually founded.