Two types of intranuclear inclusion bodies were found in the epithelial cells of renal tubules or rami ureterici of 12 psittacine birds. One type was large and stained moderately with haematoxylin, poorly with eosin and contained a few granules which stained with haematoxylin. The other was medium in size, circular, almost filling the entire nucleus or irregularly shaped with a clear halo, and stained homogeneously with eosin. Ultrastructurally, the large inclusions consisted of virus particles and fine filamentous materials. The particles exhibited an oval or hexagonal configuration, ranging from 55 to 88 nm in diameter, morphologically characteristic of adenovirus particles. The medium-sized inclusions were composed of aggregates of fine granules. The adenovirus infections were regarded as opportunistic infections.