Satellite association (SA) in lymphocytes obtained from women was found in 89.9% of cells after 48 h in culture and in 66.1% of cells after 96 h. After 48 h, 33.7% of acrocentrics participate in SA, whereas 30.7%, and 17.7% participate after 72 and 96 h. Prophase through prometaphase nucleoli were found in 26.8% of cells after 48 h and in 13.1% of cells after 96 h. SA and mitotic nucleoli are most common in 48 h cultures, and both decrease with increasing in vitro duration. These findings suggest a relationship between nucleolar persistence and SA.