The development of long-term space thermal management systems has informed research into the influence of gravity on boiling. This work explored the influence of gravity on the hydrodynamics and heat transfer of boiling flow. Experiments were carried out using two test loops each consisting of a 6 mmID transparent cylindrical test section. Upward (+1░g) and downward (−1░g) flow boiling experiments were carried out in the laboratory while microgravity (μg) experiments were carried out during a parabolic flight campaign. The results of flow visualisation showed significant influence of gravity on the flow patterns and the influence of gravity was generally limited to mass flux, G≤400kg/m2s and/or vapor quality, x≤0.35. In all three gravity conditions, the measured heat transfer coefficient was influenced by heat flux, mass flux and/or vapor quality. For liquid Reynolds number, Relo≤2000(G≤150kg/m2s) and boiling number Bo<0.002 the measured heat transfer coefficient was highest in −1g flow and lowest in μg flow but becomes comparable at Bo>0.002. A correlation for predicting microgravity heat transfer coefficient was proposed in this work and the proposed correlation predicted 100 % of the μg data in the current work within ±20%, predicted nearly 100 % of the μg data of Ohta et al. (2013) within ±30% and around 85 % of the μg data of Narcy (2014) within -20 % to +50 %. A correlation for predicting the gravity dependent regime as it relates to heat transfer coefficient in +1g and μg flows was also proposed in this work. The proposed criterium correctly predicted over 85 % of the gravity-dependent heat transfer coefficient in the curre