Liquid immiscibility data in known binary oxide systems are analyzed in relation to three fundamental aspects. Immiscibility in glassforming systems is related to differences in ionic field strengths or electrostatic bond strengths between the network cation with oxygen and the modifier cation with oxygen. If this difference is too small or too large, immiscibility is not present. Analysis also indicates that immiscibility is not to be expected in binary phosphate and vanadia systems. Factors governing the extent of immiscibility are essentially unrelated to its occurrence; in borate and silicate systems, immiscibility is inversely correlated with the number of oxygens per modifier cation in the modifier‐rich liquid. Temperature of the monotectic almost always lies between the melting point of the glass former and the first compound beyond the immiscibility gap. Properties of the monotectic, such as the primary phase under the two liquids and location of the eutectic, are fixed according to whether the monotectic temperature is above or below the melting point of the glass former. Principles of immiscibility are summarize