The authors analysed 1,528 "genuine" single premature births, between the 28th and 36th weeks of pregnancy and over a period between 1975 and 1979, with the view to establishing clinical manifestations of nutritive, respiratory, and hormonosynthetic disorders of the placenta as possible causes of prematurity. A high percentage of hypotrophic prematurely born infants (birth weights being 10. bis 5. and below 5. percentile) and even more latent nutritional deficiency in eutrophic prematurely born infants (average weight being below the 50th percentile in all weeks of pregnancy) seem to suggest the existence of a relationship between prematurity and nutritive placental insufficiency. Retardation of growth was found to aggravate along with growing age of gestation, but it was not found to result from previous tocolysis. Prematurely born infants are extremely endangered by reduced respiratory functionality of the placenta under the stress of birth, but this endangerment cannot be equally established before labour, with premature birth imminent.--Deficiently nourished foetuses are exposed to dangers of prepartum and intrapartum respiratory complications, even in cases of premature birth. These risk is likely to worsen along with aggravating impairment of nutritional functionality of the placenta. The effects of nutritional and respiratory placental insufficiency on acidosis morbidity, RDS incidence, and overall mortality (stillbirths and neonatal mortality included) of prematurely born infants are described and discussed. Biochemical hormone investigations have pointed in the direction of latent functional impairment of the placental or of foetoplacental unity in cases of prematurity at large. The morphological functionality of the placental villus trophoblast was found to be impaired in all cases so far reviewed, whatever the established clinical causes had been. This seems to be an important foundation for the concept of relationship between prematurity and placental insufficiency.