Ferric and magnesium stearate Langmuir-Blodgett films (1) deposited on silica glass were studied by variable-energy positron beam. Positrons signal the presence of the him even after deposition of only 3 monolayers. A signal with 3 and 9% higher S parameter values are characteristic for the ferric and magnesium stearate films, respectively. In addition, positrons were found to be sensitive to the chemical structure of the layers, The results suggest that positron beams could be promising probes of the thickness, composition, and adhesion of Langmuir-Blodgett films.