This evaluation of techniques, apparatus, and dedicated facilities for
measurement of very low levels of radioactivity is addressed to the l
arge community of researchers who use radioactive tracers, make activa
tion analyses, etc, and may occasionally face the problem of measuring
an activity well below the level accessible with standard commercial
equipment. Emphasis is put on the instrumental gamma-spectrometric ass
ay of complex mixtures of radionuclides, on the spectrometric measurem
ents of alpha activities in relatively massive samples, and on countin
g spontaneous fission events in samples of large mass and/or volume. A
list of institutions and agencies which are active in developing low-
level counting methods is given.