PIP: Results are presented of a study of 19,853 deliveries prospectively studied from January 1969-May 1970 in a teaching hospital maternity ward in Chile to determine relationships between age, parity, and maternal and fetal mortality. The frequency of toxemia of pregnancy remained more or less constant from 15 years to 29 years but above 29 years it progressively increased, until by age 40 it was twice the level found in women under 30. Highest levels were found in nulliparas and multiparas with 7 or more births. Lowest incidences were found in parities 1-2. The incidence of hypertensive syndrome increased in relation to age in all parity groups when age and parity were jointly analyzed but the influence of parity was not similary consistent. There was a clear tendency to increased incidence of breech births with age, with lowest frequency in the 15-19 age group and almost 7 times the frequency among those 35 and above. The incidence of breech births also increased with parity. Postpartum hemorrhage due to uterine inertia was almost constant from 15-29 years, doubled in the group from 30-39 years, and was 3 times higher in the group 40 years and above. Postpartum hemorrhage was least common in nulliparous women and increased steadily before reaching its maximum among women of parity 7 or more. The incidence of placental hemorrhage remained almost constant through 29 years and thereafter increased but not progressively. The frequencey of placental hemorrhage was lowest in parity 1 and 2, moderately higher in parities 0, 3, and 5, and highest in parities 5 and above. The highest incidence of fetal malformation was among mothers aged 40 or above. Between 14-34 the incidence did not vary. The rate doubled for mothers under 15 and in those aged 35-39, and quadrupled among in mothers also higher among women over 40. No correlation was observed between parity and neonatal mortality. Late fetal mortality remained almost constant through 34 years and almost doubled for the group 35-39. The highest incidence was among mothers over 40. Late fetal mortality declined from parity 0 to parity 1-2, and thereafter increased steadily with parity.