A comprehensive study was carried out in regards to flow patterns and void fraction in horizontal two-phase flow. Five flow patterns were observed in the course of experimentation through the collection of 530 data points in an air-water system. The flow pattern map developed was shown to be comparable with the popular maps within reasonable deviations. This map may be used as a reference for future studies on the setup. 184 data points covering the void fraction range of 0.14 to 0.84 were collected. This dataset of known accuracy forms a reliable resource for future work. 69 void fraction correlations were tested against a combined database of 1505 points from present study and external sources. Different correlations applicable to different flow patterns and void fraction ranges were determined. The best overall performing void fraction correlations were determined to be those by Woldesemayat & Ghajar (2007) and Minami & Brill (1987). The correlation of Woldesemayat & Ghajar (2007) was also found to be the best correlation for the data collected in the present study.