SummaryAn analysis of 96% of Israeli live births, 1968–70, gives a mean birth weight of 3299 ± 543 g with 5·7% weighing less than 2500 g. The mean values increased from 3193 ± 510 g for first born to 3469 ± 604 g for tenth and subsequent births.There were significant differences between the mean birth weights, adjusted for birth order, of the different ethnic-origin groups. Infants of Jewish immigrants from North African countries weighed 3356 g followed by Christian Arabs (3337 g), Israeli-born Jews (3310 g), immigrants from Western countries (3303 g), Moslem Arabs (3251 g), Druze (3244 g) and immigrants from countries of Asia (3223 g).For the Jewish groups, the differences were diminished in the second generation of Israeli-born but those descended from Asian immigrants continued to be the lighter group.In order to determine the extent to which these differences are truly ‘ethnic’ further analyses of more homogeneous groups will be necessary taking into account a number of other demographic and socio-economic variables. (Summary in Hebrew, p. 58.)