The knowledge of linear energy transfer (LET) spectra of charged particles is important for better estimation of the biological efficiency of neutron radiation therapy. A novel approach to simultaneous micromacro dosimetry with a semiconductor MOSFET probe has been developed. The response of a MOSFET probe to alpha particles and gamma radiation showed the possibility of separately measuring the low and high LET components in a mixed gamma-neutron radiation field. The proposed new approach to micro- macro dosimetry was studied in the fast neutron beam at Harper Hospital, Detroit, Michigan. By using a single MOSFET sensor, the pattern of energy deposition of the secondary charged particles in a micron-size silicon volume was measured simultaneously with the average absorbed dose. A depth-dose distribution profile in a water phantom was measured. Good agreement was observed between the neutron depth-dose distribution obtained by a MOSFET in the integral mode and a tissue-equivalent ionization chamber.