The peer support counseling intervention improved breastfeeding duation and initation in the two trial clinics in Washington State. "The likelihood that women enrolled in WIC would initiate BF at Public Health Seattle and King County Clinics increased by 3%, whereas those in Catholic Health Initatives Franciscan Medical Group clinics increased by 6.8%. Women receiving services in smaller PHSKC clinics (n < 60 women) were likely to breastfeed their infants at >1 week."