This paper presents the results of an experimental study of the shape of long isolated bubbles similar to those observed in horizontal and inclined intermittent flows by using parallel-wire probes and photography.It was shown that the shape of bubble nose

body and tail depended on Froude number and pipe inclination angle

whereas the shape of bubble tail depended on bubble length as well.The photographic study showed that bubble tail changed from staircase pattern to hydraulic jump

corresponding to the transition from plug to slug flow

with increasing Froude number and bubble length.The inclination angle had strong influence on the shape of tail

which would lead to the transition from plug to slug flow.The transition in an upward pipe occurred at lower superficial gas and liquid velocities compared to that in a downward pipe.The bubble shape from nose to tail was reversed in downwardly inclined pipe at low Froude number.