A method for monitoring the condition of oil contained within a gearbox of a wind turbine, the method comprising: receiving a signal corresponding to a measurement of an oil parameter of the gearbox; comparing the measurement to a predetermined limit for the oil parameter; assigning a severity level based on the comparison of the measurement to the predetermined limit; and characterised by: determining a recommended course of action for the wind turbine based on the severity level, by receiving a signal corresponding to a second measurement of the oil parameter; and comparing the second measurement to the predetermined limit; the method further comprising continuing operation of the wind turbine in the event that the second measurement does not exceed the predetermined limit; conducting a statistical analysis of at least the oil parameter in the event that the second measurement exceeds the predetermined limit; comparing results of the statistical analysis to an allowable trend limit; and shutting down the wind turbine in the event that the results of the statistical analysis exceed the allowable trend limit or continuing operation of the wind turbine in the event that the results of the statistical analysis do not exceed the allowable trend limit. receiving a signal corresponding to a measurement of an oil parameter of the gearbox; comparing the measurement to a predetermined limit for the oil parameter; assigning a severity level based on the comparison of the measurement to the predetermined limit; and characterised by: determining a recommended course of action for the wind turbine based on the severity level, by receiving a signal corresponding to a second measurement of the oil parameter; and comparing the second measurement to the predetermined limit; the method further comprising continuing operation of the wind turbine in the event that the second measurement does not exceed the predetermined limit; conducting a statistical analysis of at least the oil parameter in the event that the second measurement exceeds the predetermined limit; comparing results of the statistical analysis to an allowable trend limit; and shutting down the wind turbine in the event that the results of the statistical analysis exceed the allowable trend limit or continuing operation of the wind turbine in the event that the results of the statistical analysis do not exceed the allowable trend limit. determining a recommended course of action for the wind turbine based on the severity level, by receiving a signal corresponding to a second measurement of the oil parameter; and comparing the second measurement to the predetermined limit; the method further comprising continuing operation of the wind turbine in the event that the second measurement does not exceed the predetermined limit; conducting a statistical analysis of at least the oil parameter in the event that the second measurement exceeds the predetermined limit; comparing results of the statistical analysis to an allowable trend limit; and shutting down the wind turbine in the event that the results of the statistical analysis exceed the allowable trend limit or continuing operation of the wind turbine in the event that the results of the statistical analysis do not exceed the allowable trend limit.