We present two techniques to lock a laser frequency on an atomic transition line by using an electromagnetically induced transparency (EIT) signals, which give optical and electric feedback. We employed these methods to the D-2 line of Rb-87 atoms. Spectral characteristics of subnatural linewidth EIT allow us to improve frequency stability. By optical feedback of EIT signals, we were able to obtain locking bandwidths of 12 MHz, while frequency stability was 5x10(-13) at best after 100 s of integration using a frequency modulation technique. (C) 2004 American Institute of Physics.