BACKGROUND/OBJECTIVES: We aimed to assess the effects on mild morbidity of a richly micronutrient-fortified complementary/replacement food given to Zambian infants aged 6-18 months. Previous results (The Chilenje Infant Growth, Nutrition and Infection Study Team, 2010) showed an increase in the rate of hospital referral for pneumonia in the same cohort. SUBJECT/METHODS: A total of 743 six-month-old healthy Zambian infants were randomised to receive either a richly or a basal micronutrient-fortified porridge for 12 months. Mild morbidity was defined as an illness that did not cause death or require hospitalisation and was diagnosed on clinical examination at scheduled visits. RESULTS: There was no evidence of an effect of trial arm on overall mild morbidity during the study (odds ratio (OR)=1.04, 95% confidence interval (CI)=0.90, 1.20, P=0.62). Infants in the richly fortified arm had significantly more visits in which they were diagnosed with lower respiratory tract infections/pneumonia (OR=1.65, 95% CI=1.06, 2.59, P=0.03) and fewer visits in which a diagnosis of urinary tract infection was made (OR=0.43, 95% CI=0.21, 0.87, P=0.02). Maternally reported symptoms were similar between trial arms. CONCLUSION: Compared with the basal diet, the richly micronutrient-fortified food was associated with more episodes of lower respiratory infections/pneumonia diagnosed at scheduled visits, which reinforces our previously reported findings of a higher incidence in hospital referral for pneumonia.