The weight penetrometer is a light weight device and can be easily deployed on slopes not accessible to conventional exploratory tools such as drill rigs or cone penetrometers. The weight penetrometer is particularly useful for investigating the failure surfaces of the rain-induced, shallow landslides common in the residual soils and weathered rocks in the tropics. Several case histories are presented in the paper, where the sliding surfaces established from the weight sounding tests agree closely with the surface traces of the slides and with observations made in trenches dug at the base of the slides.