The unconfined compression strength qu is foundamental soil parameter to estimate the strength of marine clays. Because of the distrubance during bouring and sampling, qu value generaly has the large scatter. To study the characteristics of the scatter, the analysis of the soil investigation results of two case records and the series of the laboratory tests are carried out.
　The main conclusions are as follows:
　(1) Two types of sample disturbance effect the scatter of qu. One is remolding type, and the other is fissure type.
　(2) With remolding type disturbance, the secant modulus E50 decreases more than qu. While, with fissure type disturbance, the reduction of E50 is as much as that of qu.
　(3) Two type of sample disturbance are observed in two soil investigation results which were carried out in Tokyo Bay and Osaka Bay.
　(4) As for the samples with fissure Type disturbance, the undrained unconsolidated triaxial test gives better estimation of the strength than unconfined test.