ENThe Palace of the Grand Dukes of Lithuania erected in the Renaissance style at the 16th century was situated in the centre of the Lower castle in Vilnius. The palace was demolished in the early 19th century. The 18th century plan and drawings show that it consisted of four buildings that enclosed a courtyard of an irregular quadrangular form. Only a part of the eastern building reconstructed in the 19th century survived. In 1986 the Institute of Planning of Monument Restauration started the archaeological and architectural investigations that proved to be awarding. It was decided to carry out the research of all the territories of the palace. In 1988 the Institute of History of Lithuania (Academy of Sciences) was instructed to proceed with the research. A report on the investigations of 1988 has been published*. In 1989 the archaeological investigations were carried out west of the southeastern corner uncovered in 1988. Two more basements (D and E) and a part of the courtyard were unearthed. They yielded various architectural details, tiles, iron artefacts, etc. The present book is a report on the archaeological and architectural research work of 1989. Historical and monographic records are scarce. [...].