It is well known that most of the emissions from TWC cars are emitted during the cold start period. These emissions increase considerably at decreased ambient temperatures. To reduce cold start emissions an engine block heater may be used. In this present study the effects on the exhaust emissions of using a block heater were investigated. The exhaust was characterized by both regulated and some unregulated exhaust components. The car was tested according to the FTP-75 test procedure for regulated emissions at +22, +5 and -15°C ambient temperatures. At +5°C additional analysis of Polycyclic Aromatic Compounds (PAC) and 2,3,7,8-tetrachloro dibenzo-p-dioxin (TCDD) receptor affinity test was carried out.The test results showed reductions of CO and HC emissions when using a block heater. The reductions of these emissions were 60 and 65% respectively at the lowest ambient temperature investigated. NOx emissions were less affected and even increased marginally in some cases. The results also showed reductions of particulate emissions in the first phase of FTP-75, by 55% at the lowest ambient temperature. PAC emissions at +5°C are shown to decrease even more than suggested by the reduction of HC and particulate emissions, compared to the results without a block heater. The TCDD tests indicated similar results as for PAC. Real time measurements of the emissions indicated that most of the emissions were emitted in the first two km of the test cycle.This investigation shows that the use of a block heater has a potential to reduce harmful emissions from gasoline fueled cars at low ambient temperatures.