The key feature of organic soils is the acquaintance of organic matter content, which determines the possibility of their classification and possible usefulness for building purposes. Information included in Eurocode 7 (PN-EN 1997-1:2008; PN-EN 1997-2:2009), new classification standards (14688-1, 2:2006) and specifications (PKN-CENISO/TS 17892:2009) are general and do not specify which method should be applied to determine organic matter content. Therefore, the loss on ignition method according to the Polish standard (PN-B-04481:1988) is often used in Poland, although the standard guidelines are not precise enough, because the temperature range suggested for soil roasting is wide, from 600°C to 800°C, and the time recommended for sample roasting is 4 hours and additionally from 3 to 4 hours. The ambiguity of standard conditions for tests was the basis for undertaking research in order to verify the influence of leading parameters, i.e.: temperature and time, on the results of roasting. The tests were conducted on organic soil samples. A number of tests were conducted for temperatures, from 550°C to 850°C and for different time periods from 3 to 9 hours. In total, 756 samples were tested in 63 testing series. The test results revealed that the only main parameter to decide about the outcome of a roasting test is temperature. This, in turn, has a practical meaning, as it enables the test procedure to be facilitated and the roasting process to be shortened.