The three lacertid lizards species of the Iberolacerta genus, which have recently been described or recognised as different species, are reptiles that live strictly at the highest altitudes in Europe, from elevations of near 1900 up to more than 3000 m a.s.l. in the Pyrenees (Spain, Andorra, France). In this paper, the reproductive cycle and reproductive characteristics of these species are described for the first time. Data were obtained from field studies carried out in different high-mountain Pyrenean locations from 1989–2002. In addition we also conducted hatching studies in laboratory. Due to the harsh climatic conditions in the high mountains the activity cycle of these species is very short, just over 4 months, from mid-May to late September or beginning of October. This affects their reproductive cycle (i.e., only one annual egg-clutch is produced), as well as other reproductive characteristics, as the existence of a very advanced embryonic development at oviposition, which is interpreted as an advanced stage in the tendency towards viviparity, and diverse life history characteristics as a very little annual growth which greatly delays sexual maturity to 4 years in males and 4–5 years in females. Clutch size correlates significantly with female snout-vent length (SVL) in all three species. The average clutch size is 2.53 eggs in I. aurelioi (the smallest species), 3.03 in I. bonnali and 3.44 in I. aranica (the biggest species). Notwithstanding the differences in egg number the three species have a similar egg volume. The incubation period in the laboratory is very short with an average of 30–36 days among the species. The low reproductive potential observed in these three species and revealed in this paper is a strongly threatening factor which, together with their extremely reduced distribution area, endangers these endemic, rare and very threatened species.