Over the past decade, the polima cytoplasmic male sterility (pol CMS) three-line and two-line systems have been developed for the production of hybrid seed in Brassica napus oilseed rape in China. The discovery of the novel pol CMS restorer line FL-204 is described here. It restores male fertility of hybrid plants in the pol CMS system, but hybrid seed production can only be carried out under autumn sowing in Wuhan in south China under moderate temperatures at flowering. The restorer cannot be used as a male for hybrid seed production in northwestern China (Gansu) under spring sowing conditions, because there it is more or less male sterile due to high temperatures at flowering. Because of this behaviour, it is referred to as a fertility temperature-sensitive restorer (FTSR) in this paper. F2, BC1 as well as double haploid populations were constructed to determine the inheritance of fertility restoration of FL-204 in the autumn at Wuhan and under spring sowing conditions at Gansu, respectively. Deviations from Mendelian genetics were observed. It was hypothesized that the change of fertility was the result of the interaction between nuclear genes [restoring gene (Rf) and temperature-sensitive genes (ts)] and the cytoplasm. The Rf gene in FL-204 was incapable of restoring male fertility of pol CMS lines under spring sowing conditions at Gansu where it is inactivated by the recessive ts gene present in FL-204. However, the ts gene(s) could be non-functional under moderate temperature conditions at flowering at Wuhan which allows full expression of male fertility in FL-204. The recessive ts gene(s) can only be expressed in plants containing the pol sterile cytoplasm. A method for the utilization of the FTSR pol CMS restorer FL-204 for the production of hybrid seed in B. napus oilseed rape is proposed.