There are often two different types of index used to determine how effected gastropods are from imposex, Vas Deferens Sequence Index (VDSI) and Relative Penis Length Index (RPLI). Data samples of Tritia nitida have been downloaded from IVL’s database and were collected around the Swedish west coast. Regression analysis and T-test were performed on all the data collected and at three different locations (Gothenburg, Lysekil and Strömstad) to analyse how the VDSI, RPLI plus the index Percent Female Displaying Imposex (IMPF) were correlated with the concentration of organic tin compounds in their tissue. Results show that the Index VDSI has the strongest correlation in all the studied areas which makes it the preferable index to analyse organic tin compounds in Tritia nitida with. Result also show a stronger correlation with ∑BT (TBT+DBT+MBT) than for TBT alone at all the studied areas, which can be an indication that TBT effected the organism and then transforms to its degradation components. Significant p-values from t-tests when comparing the areas with each other also suggest that there are local variations in how Tritia nitida is affected by organic tin compounds. There is also a trend where higher concentration of ∑BT in the tissue leads to a higher correlation with VDSI (except for “3.1 Alla kommuner kombinerade).