This study was undertaken to evaluate the variable clinical expression of hemoglobin (Hb) H disease in India. For the study, alpha genotyping was done in 8 patients with Hb H disease using multiplex polymerase chain reaction and DNA sequencing. The study revealed that 4 genotypes (- -(SEA)/ -alpha(3.7), - -(SA)/-alpha(3.7), - -(SEA)/-alpha(3.7 Sallanches), - -alpha(3.7)/-alpha(3.7 Sallanches)) were responsible for Hb H disease, the alpha+ thalassemia mutation (-alpha(3.7) deletion) being the most common defect. The nondeletional mutation Hb Sallanches (alpha 2 codon 104 G ->> A) was seen in 3 cases. Two unique and novel genotypes leading to Hb H disease were characterized (- -(SEA)/-alpha(3.7 Sallanches) and -alpha(3.7)/-alpha(3.7 Sallanches)). Because a majority of patients with Hb H disease do not have severe manifestations, prenatal diagnosis is usually unwarranted in India.