Out of 2985 individuals referred for carrier detection, analysis of SMN1 copy numbers among 1225 non-relative Iranian individuals (Mean age (SD) = 30 (± 7) years) with no prior history of SMA, showed that 5.55% (n = 68, CI = 0.95%, 4.36–7.02) had one copy of SMN1 being a carrier for the disease. The gene discussed is SMN1; the disease is proximal spinal muscular atrophy.