Abstract ABSTRACT. Kanawati, A. A., McLaren, D. S. and Darwish, O. (Nutrition Research Program, School of Medicine, American University of Beirut, Beirut, Lebanon). Failure to thrive in Lebanon. IV. Longitudinal health and growth data. Acta Paediat Scand,63: 849, 1974.—Pre‐school age Arab children of low socio‐economic standard living in urban and suburban areas of Lebanon were divided into Thrive and Failing to Thrive groups according to an Index of Thriving. They were matched for age and their young siblings were also studied. Various somatic measurements were made and. health‐related data collected on three occasions over a period of approximately three years. Notable among the findings were (1) the very low mortality rate, (2) evidence of considerable spontaneous catch‐up growth in the Failing to Thrive group, (3) a high rate of obstetric experience in both groups, greater in the Failing to Thrive, and (4), frequent occurrence of infections with a tendency to delay vaccination, especially in the Failing to Thrive group, as a probable consequence.