Whether insiders can use informational advantage when purchasing or selling their company stocks to generate cumulative abnormal returns (CAR) has shown different results in several markets. The Swedish market is yet to be extensively examined, and this thesis aims to understand how insiders in the OMXS30 companies perform when testing CAR and if there exists an information asymmetry. A predicted return is generated through the market model to calculate CAR, and the same index OMXS30 is combined with stock return data. We conducted an event study through Stata to match the transactions with a particular trading day to see how the insiders' transaction yielded CAR. We find that significant CAR exists for all insider groups for various event windows and find a difference in significant CAR for both genders and insider positions. The results were robust when we changed to a new market index as the independent variable in our regression analysis. The results align with previous literature, stating that insiders generated significant CAR from insider trading and differences between insider position and gender (Jeng et al. 2003; Jiang & Zaman, 2010; Lasfer & Ye, 2023). The findings can be used for regulatory purposes when investigating information asymmetry.