Since the beginning of the 20th century an increasing number of people in the Western civilization suffer of obesity, diabetes and atherosclerosis as a consequence of impaired neutral lipid metabolism. Triacylglycerols (TAG), which are the major storage compartments, accumulate and can lead to various cellular defects and diseases. The yeast Saccharomyces cerevisiae is a widely accepted model for the biochemistry and molecular biology study of neutral lipid metabolism. In yeast, neutral lipids are stored in so called lipid droplets (LD). The core of these organelles contains TAG and steryl esters (STE). TAG are mobilized by three TAG lipases. In the yeast, the main TAG lipases are Tgl3p, Tgl4p and Tgl5p. In my master thesis I focused on regulatory aspects of the TAG lipases Tgl4p and Tgl5p. We investigated gene expression, protein level and localization of these enzymes under different conditions. In the absence of LD gene expression and protein level were not reduced and the two TAG lipases localized to the ER. In wild-type, Tgl4p and Tgl5p are located to LD and to the ER. Moreover, gene expression and the protein levels of Tgl4p and Tgl5p were tested in the double deletion strains tgl3?tgl5? and tgl3?tgl4?, respectively. Interestingly, a reduction of TGL4 in a tgl3?tgl5? deletion strain, but an increase of TGL5 in a tgl3?tgl4? deletion strain was observed. Moreover, the gene expression levels of TGL3, TGL4 and TGL5 in different growth phases were examined. The highest mRNA concentration of all three TAG lipases was found during the logarithmic phase of growth. Especially the mRNA concentration of TGL3 was high compared to the relative gene expression level of TGL4 and TGL5. In summary, this study demonstrated that the network of TAG mobilization in yeast catalyzed by Tgl3p, Tgl4p and Tgl5p is subject to complex regulation.