The present study investigated longitudinally the performance development of a multigenerational sample of competitive swimmers. The aim of the study was to provide unique insight into the junior towards senior performance development of those few who reached top-elite level. Season Best Times (SBT) of 100m freestyle performance of international swimmers, (1.305 males, aged 12-26 and 1.841 females, aged 12-24) competing in at least five seasons between 1993 and 2018, were corrected for the prevailing world record (WR). Swim performance was defined as a relative measure: relative Season Best Time=(SBT/WR)*100. Based on rSBT, four performance groups were defined: top-elite, elite, sub-elite and high-competitive.Univariate analyses of variance showed that male top-elite swimmers outperformed high-competitive swimmers from the age of 12, sub-elite swimmers from the age of 14 and elite swimmers from the age of 18 while female top-elite swimmers outperformed high-competitive and sub-elite swimmers from the age of 12 and elite swimmers from the age of 14 (p<0,05). Frequency analysis showed that male top-elite swimmers for the first time achieved top-elite level between the 17 and 24 years old (mean age of 21) while female top-elite swimmers started to perform at top-elite level between the 14 and 24 years old ( mean age of 18).Male and female top-elite swimmers are characterized by a high performance level from 12 years on and progressively outperform swimmers from similar age. However, this goes together with a large variety in the individual pathways towards top-elite level within and between sexes.