The present study is based on 4871 Salamandra infraimmaculata half-sib larvae belonging to 74 cohorts born in the laboratory to individually identifiable females during the study period 1974–1998. Some cohorts (37%) included between 50 and 100 larvae, 40% of the cohorts had <50 larvae and 23% had >100 larvae. Some larvae (48.4%) were born early during October–November; the remainder were born later in the season. 17.7% of all larvae were born during the third week of December. About 3% of the larvae studied here were born dead either malformed or aborted before they were ready. On one occasion, larvae were born alive free of their yolk sac. There is a significant variability in the mass of newborn larvae. The number of larvae born in cohorts of five females (F-65, F-69, F-81, F-83 and F-114) varied over the years. The variability may be due to the fact that the larvae may be of different paternal origin. This is reflected later in their differential growth and metamorphic timing. There was no relationship between cohort size and female's age. The significance of the larval period for survival of the adult salamander is discussed.