Ages & Stages Questionnaires (ASQ) is a flexible system that allows programs to choose the frequency of screening based on what works best with the program’s goals and capabilities. There are no set requirements for use of specific age intervals. The developers do recommend that programs screen on a regular basis, rather than just once, to detect delays that may develop as children grow. For children birth to 24 months, screening every 4–6 months is adequate. For children 2–3 years, every 6 months is adequate. For children 4–5 years, once or twice yearly is adequate.