We have examined in mice the immune adherence (IA) reactivity and the fate (clearance kinetics and organ distribution) of a variety of preformed and nascent soluble antibody/125I-DNA immune complexes prepared at antibody excess. Parallel studies of the clearance kinetics and organ deposition of free DNA were also conducted. Preformed immune complexes prepared with large dsDNA bound to mouse platelets in vivo and exhibited clearance kinetics in general agreement with our previous observations in rabbits. Very little kidney deposition was evident for these immune complexes, but three to four times as many counts were found in the kidneys when free DNA was injected. Nascent immune complexes did form in the circulation, but in contradistinction to our previous studies of nascent immune complexes in rabbits and rhesus monkeys, these immune complexes did not demonstrate IA and had clearance kinetics and organ distributions intermediate between the preformed immune complexes and free DNA. Thus, complement-fixing antibody/DNA immune complexes that could form in the circulation might be cleared both via immune complex recognition mechanisms and via DNA recognition mechanisms. The role of IA in modulating the organ deposition of complement-fixing immune complexes is also discussed.