Immune electron microscopic procedures for the detection of adenovirus type 7 directly in throat swab specimens from patients are described. Nineteen of 25 throat swab samples, known to be positive for adenovirus type 7 by isolation of virus from tissue culture, were shown to contain aggregates of adenovirions coated with antibody. Sensitivity tests of the immune electron microscopic method showed that as few as 16 to 32 tissue culture infective doses of virus could be detected by the direct immune electron microscopic technique. It was also demonstrated that aggregation of virus-antibody complexes could be further enhanced by use of anti-immunoglobulin G sera (indirect immune electron microscopic procedures). These results demonstrate that examination of patient specimen by immune electron microscopic procedures is a feasible and rapid method for adenovirus detection and suggest that it could be applied as a routine laboratory procedure for the diagnosis of other virus infections.