The pattern of initial clinical symptoms and signs developing in a representative sample of 305 children with homozygous sickle cell (SS) disease diagnosed at birth was analyzed. Specific symptoms were present by age 6 months in 6% of the group, and had developed by the first to eighth birthdays in 32%, 61%, 78%, 86%, 90%, 92%, 94%, and 96%, respectively. Inclusion of nonspecific symptoms in the analysis led to earlier recognition by a mean of 3 months in the first year and by a mean of approximately 1 year between the ages of 2 and 4 years. Dactylitis was the most common initial symptom, noted in 40% of the group overall and in 50% in the first 2 years. Painful crisis was the first symptom in more than one fourth of the patients and was the most frequent symptom after the age of 2 years. Acute splenic sequestration led to presentation in one-fifth of the group overall and in one third of patients younger than 2 years. The most common nonspecific symptom was pneumonia. There was a significant trend of earlier presentation in children with low fetal hemoglobin levels. The age at presentation did not appear to be affected by alpha-thalassemia status.