Abstract. The aim of this study was to describe the relationships among lambs' birth weight, survivability traits, growth performance, and selected factors in Suffolk lambs kept under a specified extensive management system. Data were collected regarding 1012 Suffolk lambs born during a 3-year period (2012–2014) in one flock. Statistical analyses were conducted using the SAS and CANOCO program software. Birth weight was found to be an important factor influencing survivability and growth performance traits. Lambs with too low a birth weight (< 2.9 kg) had the worst results of practically all the survivability and growth performance traits. A significantly lower percentage of live-born lambs (5.2 to 6.1 %; P < 0.05) was also observed amongst overweight lambs at birth (> 6.0 kg) compared to lambs with a birth weight of 4–5.9 kg. Generally, the highest results of growth performance traits were detected in groups of lambs with a birth weight of 5.0–5.9 and 6.0–9.0 kg. Therefore, the optimal birth weight of Suffolk lambs was in the range of 5.0 to 5.9 kg in the evaluated flock management system. Litter size was found to be the dominant factor influencing birth weight, survivability, and growth performance traits, such that singles tended to have the highest birth weight and growth performance traits, while higher survivability traits were found in twins. The results of multivariate relations also clearly indicated that the selection of lambs should be focused on twins with regard to the monitoring of mature ewes' live weight at mating, which helped to improve the lambs' survivability traits, in particular. The monitoring of ewes' mature live weight at mating should also serve as a tool for flock management to shorten the lambing period in the flock and to improve the birth weight and growth performance traits of lambs. The mature ewe body condition score at mating should be monitored to ensure that lambs are adequately meaty and fatty. This study confirmed the importance of keeping records of birth weight and suggested practical implications of some important factors when improving flock profitability.