The present paper describes the development of an instrumented impact cone penetrometer for a direct measurement of in situ strength properties of a soil target. The developed penetrometer, in addition to providing acceleration signatures (as obtained by previous investigators), is capable of recording cone thrust and local side friction simultaneously and continuously. The procedures have been outlined for estimating in situ strength properties and soil type of the target materials throughout the penetrated depth from the output records of these sensors. Typical test results generated from an on-going experimental program aimed at providing the data for (1) understanding the penetration mechanism, (2) development of penetration theory, and (3) designing the penetrometer for field tests, i.e. in situ testing of ocean floor soils, are also presented.