Fatty acid methyl esters (FAME) are considered to be promising and prospective alternative fuels for diesel engines. They can be produced from vegetable oils and animal fats by transesterification of triacylglycerols with methanol. This paper presents the results related to the stability of FAME from aging tests of FAME in the period of 7 months. The FAME were prepared from four oil types, which were finally treated, stabilized, and stored in a different way. The results show that lower ester content in freshly prepared FAME, having at the same time a good conversion, is related to degradation of the oil from which the FAME were prepared. The stabilities of FAME samples prepared from old oils and used frying oils are lower than the stability of FAME samples prepared from fresh oils. Insufficient conversion of FAME itself does not have negative influence on its stability. After final distillation treatment, FAME exhibits lower stability when compared with the sample treated in the standard way. However, they are very sensitive to the presence of an antioxidant; the addition of 0.04 wt % of pyrogallol ensures high FAME stability.