In the proposed project, during a three-year period, 60 individuals fulfilling prodromal criteria will be randomly entered in a 16 week parallel group, double-blind, placebo controlled trial with 2 gr/day sarcosine, with an optional 8 week open-label extension. Clinical, neurocognitive, electrophysiological, amino acids (i.e. glycine, serine, glutamate) levels and genetic assessments will be performed during the study. The specific aims of the proposed project are: 1) to assess the efficacy and safety of sarcosine as active treatment for prodromal symptoms, 2) to assess sarcosine effects in terms of relevant amino acids serum levels, neurocognitive performance and relevant brain electrophysiological parameters and 3) to supply preliminary data in regard to the capacity of sarcosine treatment to delay/prevent conversion to full blown psychotic disorder. The overall importance of the proposed project consists of its potential to lay the foundations for an innovative type of treatment for schizophrenia prodromal states.