The primary objective of the present study was to assess the effect of DHA and arachidonic acid (ARA) supplementation of infant formulas on the incidence of respiratory illnesses during the first year of life. Enrolment for this multicentre prospective open-label 12-month observational study was conducted from 2002 to 2003 and included 1392 children from 357 Spanish paediatricians (the GENERACIÓN Study Group). Infants were assigned in the proportion 4.4:1 to receive a formula supplemented with 3.2 g DHA and 6.4 g ARA/kg or a low or non-supplemented control formula. Eligible infants were healthy, born at a gestational age that exceeded 36 weeks and non-breast-fed. Infants were to visit the paediatrician at baseline and months 1, 3, 5, 7, 9, and 12. At each subsequent visit records were taken of: anthropometric measurements; month of introduction for gluten-free cereal, gluten, fruits, vegetables, meat, fish, egg yolk, whole egg, cow's milk and legumes; the occurrence of clinical symptoms associated with common ailments in infancy. Results of the main objective have been published elsewhere(Reference Pastor, Soler, Mitmesser, Ferguson and Lifschitz^1, Reference Pastor, Soler, Ferguson and Lifschitz²), and showed a significantly lower incidence of bronchitis or bronchiolitis in DHA+ARA-fed children. The secondary objective was to determine the adherence to paediatricians' recommendations to guidelines(^{3, 4}) on the introduction of complementary foods to the infant's diet. Achievable Benchmarks of Care (ABC)^® ratios were also calculated to determine the standards of excellence attained by the 10% of top performers(Reference Weissman, Allison and Kiefe⁵) and identify areas for improving adherence to guidelines on the introduction of complementary foods(Reference Kiefe, Allison, Williams, Person, Weaver and Weissman⁶). The Table summarizes the findings from the study. Overall, the adherence was appropriate for most recommendations, but some recommendations need to be reinforced, such as the introduction of fruits, fish, cow's milk and legumes.