Headspace and aqueous phase solid phase microextraction (SPME) mehtods for the analysis of butyltin compounds in sea water were evaluated and compared. The method detection limit (MDL) for monobutyl- (MBT), dibutyl- (DBT), and tributyltin (TBT) in sea water were detected as 3.5, 3.8, and 3.8 ng/L, respectively, by the headspace SPME method. On the other hand, the MDL for MBT, DBT, and TBT in sea water were detected as 19.2, 20.4, and 31.7 ng/L, respectively, by the aqueous phase SPME method. Butyltin compounds in seawater collected from different harbors in Taiwan had MBT in the range of 5.5-51.9, DBT