This study evaluates the relationship between a field-based 8-min time trial (8MTT) and physiological endurance variables assessed with an incremental laboratory test. Secondly, lactate thresholds assessed in the laboratory were compared to estimated functional threshold power (FTP) from the 8MTT. Nineteen well-trained road cyclists (aged 22 ± 2 yr, height 185.9 ± 4.5 cm, weight 72.8 ± 4.6 kg, VO2max 64 ± 4 ml·min-1·kg-1) participated. Linear regression revealed that mean 8MTT power output (PO) was strongly to very strongly related to PO at 4 mmol[BULLET OPERATOR]L-1, PO at initial rise of 1.00 mmol[BULLET OPERATOR]L-1, PO at Dmax and modified (mDmax) (r = 0.61 – 0.82). Mean 8MTT PO was largely to very largely different compared to PO at fixed blood lactate concentration (FBLC) of 2 mmol·L-1 (ES = 3.20) and 4 mmol·L-1 (ES = 1.90), PO at initial rise 1.00 mmol[BULLET OPERATOR]L-1 (ES = 2.33), PO at Dmax (ES = 3.47) and mDmax (ES = 1.79) but only trivially different from maximal power output (Wmax) (ES = 0.09). The 8MTT based estimated FTP was moderate to very largely different compared to PO at initial rise of 1 mmol[BULLET OPERATOR]L-1 (ES = 1.37), PO at Dmax (ES = 2.42), PO at mDmax (ES = 0.77) and PO at 4 mmol[BULLET OPERATOR]L-1(ES = 0.83). Therefore, even though the 8MTT can be valuable as a performance test in cycling shown through its relationships with predictors of endurance performance, coaches should be cautious when using FTP and PO at laboratory-based thresholds interchangeably to inform training prescription.