During the Upper Triassic, in the western part of Hungary the paleogeographical conditions were favourable for the deposition of formations with high organic matter content. The best reference section of the Kossen Formation can be found in the Keszthely Mountains at Rezi Village: the borehole Rzt-1. The alginite sequence of the Kossen facies in he borehole Rzt-1 can De characterized by a moderate organic matter content (average C-org = 6.1%), relatively high carbonate-rich mineral part (average C-carb = 6.1% and relatively low total sulphur content (average S-t(a) = 1.6 %. On the basis of comparison of the previous average values derived from the qualitative analysis of the alginite-bearing samples from the borehole Rzt-1 with others for other Hungarian and Slovakian alginites, it can be established that the carbonate carbon and total sulphur content is higher in the Rezi samples, than in the other Hungarian and Slovakian ones. Two changes can be observed in the distribution among the varieties of sulphur in the studied alginite samples from the borehole Rzt-1. Above the interval 181.9-199.6 m the following order: pyritic sulphur (S-p(a)) > organic sulphur (S-org(a)) > sulphate sulphur (S-SO4(a)) is characteristic. Between 199.6-233.3 m the order is S-org(a) > S-p(a) > S-SO4(a) and below 233.3 m repeatedly S-p(a) > S-org(a) > S-SO4(a) . According to the present and previous studies the alginite sequence of the Kossen facies may, serve as a potential oil-source rock for petroleum found in the Zala basin. Presumably, the greater than or equal to 20 % of the sulphur content belonging to the Nagylengyel-type petroleum might have originated in the Kossen Formation.