The presence of body-like structures in nuclei from interferon alpha-treated Daudi cells has been shown on the ultrastructural level, by the use of different staining methods. The degree of their rearrangement in the nucleoplasm seems to be dependent on the time of interferon treatment. Since this morphological evidence has been found to be preceded by a slowing down of RNA transcriptional machinery early upon the interferon administration, it is speculated that interferon generated signals might lead to RNP granule accumulation in the nucleus and a consequent arrangement into defined structures.