Very-high-efficiency (80%) Raman amplification of a narrow-band injected Stokes signal has been achieved in the case in which pump and Stokes linewidths are both narrower than Raman transition width. Under such conditions, the Stokes-beam amplification is obtained without line broadening, permitting the creation of widely tunable powerful monochromatic sources when tunable lasers are used. With fixed-frequency pump lasers, tunability within the Raman linewidth has also been demonstrated. With a pump linewidth much broader than that of the injected Stokes signal, a spectral compression rate up to 16 has been achieved by using this Raman amplification technique.