Primate cones maximally sensitive to short wavelength light (blue cones) have been previously identified by using indirect methods. We stained 7 wholemounted human retinas obtained from 6 female donors, using an affinity purified antibody to a 19 amino acid peptide sequence at the N-terminus of blue opsin (Lerea et al.,'89: Neuron 3: 367–376), standard PAP immunocytochemistry, and controls. Cones were counted where all outer segments could be traced to inner segments and were measured where cells were well aligned vertically.