The pre-consolidation pressure is an important parameter for the stress history and the consolidation behavior of cohesive soils. This paper presents the evaluation of oedometer test results of several clay samples (CL and CH) in terms of the Unified Soil Classification System. Almost 30 soil samples were considerably selected, which had been taken at different sites in Turkey and at various depths. Some of the samples were prepared as the remolded samples to be used in Rowe cell and consolidometer. All tests were performed using with the conventional oedometers with a ring diameter size-50mm for the certain. The objective of this research is to compare the results of pre-consolidation pressure by using the determination methods including "Casagrande", "Sridharan", "Tavenas" and "Senol" methods considering various engineering properties of soils. Consequently, the results show a linear relationship between the four pre-consolidation determination methods for several clays and it may be suggested for the geotechnical engineers to consider this relationship to determine more sensitive results.