This paper reviews methods for the prediction and correlation of Newtonian viscosity for pure components and mixtures of liquid hydrocarbons and petroleum fluids, which are suited for practical engineering use. The methods reviewed were chosen because they are well known and accepted or appear potentially promising. The methods are categorized as semi-theoretical or empirical and further distinguished as predictive or correlative. The applicability and average deviations for each method are discussed, with the recommended methods identified.