Hemoglobin D-Los Angeles, a recessively inherited hemoglobin variant, has been introduced as hematologically silent in the heterozygous state. However, as its compound heterozygosity with other hemoglobinopathies may lead to a severe clinical phenotype, with hemoglobin S being the most serious, the detection of carriers is important. To clarify the hematologic picture, we assessed erythrocyte parameters in D carriers and compared values in healthy controls and beta-thalassemia carriers. Although values in D carriers, in the absence of confounding factors, significantly differed from thalassemia carriers (P<0.05 for all), they were not similar to healthy controls. Microcytosis (absent in healthy controls) (mean corpuscular volume: 80.7 vs. 83.5 fL,P=0.038) and erythrocytosis (6 times more than in healthy controls) (red blood cell: 5.2 vs. 4.7x10(12)/L,P=0.002) were detected, making questionable the true silence of the D trait.