The secant Young's modulus determined at different strain level is a key issue in the geotechnical field to predict settlement of foundations. Most research works attribute to the effect of sampling disturbance as the main source of error in the measurement of the elastic modulus performed in laboratory samples. It seems that some kind of destructuration occurs when the soil is sampled in the field and thereafter trimmed for testing in laboratory. This work presents a fundamental study performed to evaluate the sampling effect of Argentinean loess. Block samples where recovered from open trenches and tested in the lab. The program includes laboratory and field measurement of shear wave velocity, and a battery of plate load and triaxial tests. The result allow us to conclude that the sampling procedure is performed correctly, and that the effect of sampling scale may produce a misinterpretation of laboratory results as the presence of local cemented aggregates increases the value of the measured wave velocity respect to the average field velocity.