The original and extended Holub phenomenological models for pressure drop and liquid holdup in trickle flow regime systematically under-predicted frictional pressure drops at elevated pressure and at high gas throughputs. On the basis of an extensive historic trickle flow regime database and Ergun bed constants (over 4000 measurements from 34 references between 1959 and 1998), state-of-the-art correlations for shear and velocity slip factors and Ergun single-phase flow bed constants (Blake-Kozeny-Carman and Burke-Plummer bed parameters) were developed. The correlations involved combination of feed-forward neural networks and dimensional analysis. The shear and velocity slip factors were expressed as a function of the six most expressive dimensionless groups (Re-L, Re-G, Fr-L, We(L), X-L, St(L)), whereas Blake-Kozeny-Carman and Burke-Plummer bed parameters were correlated to particle equivalent diameter, sphericity factor, bed porosity, and column diameter. These correlations fed into Holub＇s phenomenological model improved noticeably the prediction of frictional pressure drop and liquid holdup in trickle flow reactors.