Few studies have investigated the performance of Holstein Friesian cattle under North African conditions. Thus, the objectives of this research were to estimate genetic parameters for milk yield (MY, kg), true herd life (THL, d), and age at first calving (AFC, mo), and to compute genetic and environmental trends for MY using information from the Ghot Al-Sultan dairy farm near Benghazi, Libya. The data set contained MY, THL, and AFC records from 1,968 Holstein Friesian first-lactation cows collected from 1986 to 2002. There were 96 sires and 1,511 dams represented in the data set. Genetic parameters were estimated using restricted maximum likelihood procedures using a 3-trait mixed model. Fixed effects were year-season (all traits) and the covariates of age at first calving (MY, THL) and lactation period (MY). Random effects were cow and residual. The relationship matrix included 2,935 animals. Computations were carried out using the AIREMLF90 program. Milk yield genetic trends for cows, sires, and dams were estimated using means of breeding values for cows, sires and dams per year as regressions of average cow, sire, and dam mean breeding values on years. The estimates of heritability for MY (0.17 ± 0.04) and AFC (0.14 ± 0.03) were low, whereas the value for THL (0.05 ± 0.04) was close to zero. The estimates of genetic correlations between MY and THL (0.22 ± 0.01), and between MY and AFC (0.19 ± 0.04) were low, and the correlation between THL and AFC was near zero (0.07 ± 0.04). The MY genetic trends were 4.11 ± 0.92 kg/yr for cows, 5.70 ± 1.12 kg/yr for sires, and 2.32 ± 0.81 kg/yr for dams. Although low, the positive MY genetic trends for cows, sires and dams suggested the existence of an effective selection program and utilization of sires with superior breeding values under Libyan conditions. Conversely, environmental trends were negative for cows, sires, and dams suggesting deterioration of nutrition and management practices during the period covered in this study.