Subjectively healthy HLA-B27 positive 1st degree relatives (n = 14) of patients with ankylosing spondylitis (AS) were investigated concerning the mass fraction of calcium (Ca), magnesium (Mg), manganese (Mn), iron (Fe), zinc (Zn), strontium (Sr) and copper (Cu) in isolated blood cells using the nuclear microprobe technique. No relative had laboratory signs of inflammatory disease defined by acute phase plasma proteins. An accumulation of Mg, Ca, Mn and Fe was found in granulocytes compared with healthy controls. In platelets there was an accumulation of Fe and a reduction of the Cu content. In erythrocytes Ca was accumulated and the levels of Mg, Mn and Cu were reduced compared with the controls. Five of the relatives had radiological signs of sacroiliitis and 1 of these had sacroiliac tenderness. Relatives with and without radiological sacroiliitis showed no differences in the cellular metal amounts. When the alterations were compared with those previously found in patients with AS, a striking similarity was noted, although the changes were quantitatively less pronounced. In contrast B27 negative 1st degree relatives (n = 11) had normal mineral amounts in their cells. However, it seems less likely that altered metal handling could play a primary role for the disease susceptibility linked to HLA-B27 since B27 positive healthy controls (n = 12) without AS in the family had normal cellular stores of the measured elements. Rather our findings indicate that redistribution of cellular metals is an extremely sensitive marker of an inflammatory process not evident by clinical symptoms or increase of acute phase plasma proteins.