Data are presented on horizontal and slightly inclined flows at +5 and -5 degrees for a 0.058 m inner diameter (i) pipe with the co-current air-water system. The prediction capabilities of existing flow regime maps were shown to be inadequate. However, the transitions for stratified ripple to role wave, for slug to blow-through-slug, for film plus droplet to stratified, and the modified maps for stratified type to slug flows all gave good prediction performance with horizontal and slightly inclined flows. The largest liquid hold-up occurred in upward flow except at high gas rates and low liquid rates where the downflow condition gave the highest liquid hold-up. The lowest liquid hold-up occurred in downward flow at low gas flowrates and horizontal flow at high gas flow rates. Hold-up prediction proved to be flow regime dependent. The inclined total average pressure drop data crossed over the horizontal data from higher to lower values with increasing gas rate at a gas rate of just under (V) over bar(SG) = 10 m s(-1). Below this gas rate the horizontal pipe gave the lowest pressure drop while above this gas rate the upwardly inclined pipe gave the lowest pressure drop. A pressure loss minimum occurred at (V) over bar(SG) = 10 m s(-1) for upward flows. Below (V) over bar(SG) = 10 m s(-1) the pressure loss for downward flow was virtually independent of gas rate being mainly due to hydrostatic head. As the gas flow approached (V) over bar(SG) = 50 m s(-1) there was very little effect of inclination on the pressure loss. Pressure drop was successfully predicted although the accompanying hold-up prediction was not always reliable.