Bax inhibitor 1 (BI-1) was originally discovered as an inhibitor of Bax-induced apoptosis; this review highlights the fundamental importance of BI-1 in a wider context, including in tissue homeostasis and as a regulator of cellular stress. BI-1 has been shown to interact with a broad range of partners to inhibit many facets of apoptosis, such as reactive oxygen species production, cytosolic acidification and calcium levels as well as endoplasmic reticulum stress signalling pathways. BI-1's anti-apoptotic action initially enables the cell to adapt to stress, although if the stress is prolonged or severe the actions of BI-1 may promote apoptosis. This almost universal anti-apoptotic capacity has been shown to be manipulated during infection with enteropathogenic and enterohaemorrhagic Escherichia coli inhibiting host cell death through direct interaction between their effector NleH and BI-1. In addition, BI-1 activity is important in a large number of cancers, promoting metastasis by modulating actin dynamics, a process dependent upon the BI-1 C-terminus and BI-1:actin interaction. Manipulation of BI-1 therefore has the potential for significant therapeutic benefit in a wide range of human diseases.