A search for ways to estimate thermodynamic properties of deeply supercooled water was undertaken to make it possible to analyze nucleation rates in droplets freezing in supersonic flow. It was found that the well-known anomalous behavior of supercooled water can be accounted for by the so-called "two-state" model that had been discredited 2 decades ago. The model was found to be viable when applied in a form closely related to one introduced by Speedy [J. Phys. Chern. 1984, 88, 3364]. Water is apportioned into equilibrium concentrations of high-and low-density components in somewhat the same way as described recently by Vedamuthu et al. [J. Phys. Chem. 1994, 98, 2222] except that criteria were imposed whereby the equilibrium constant inferred from the distribution was forced to obey the van’t Hoff temperature and Gibbs-Poynting pressure relations. It was found that the expansivity, heat capacity, and compressibility anomalies calculated by the model agreed well with those measured experimentally when the equilibrium was considered to be between relatively densely packed monomers and bulky aggregates containing five or six molecules. The model does not preclude a broader distribution of oligomers, particularly when the larger species are somewhat less bulky than the model pentamers and hexamers. An appealing feature of the model is that its results can be extrapolated to arbitrarily low temperatures, making it possible to estimate the heat and free energy of the freezing of water at the very low temperatures achieved in a supersonic flow. Results of the model are compatible with Tanaka’s recent extensive molecular dynamics simulations, which were originally interpreted as corroborating the spinodal theory. Implications are also consistent with spectroscopic and X-ray scattering experiments. In addition, the model has something to say about Turnbull’s relation for estimating interfacial free energies and their temperature dependence. Strengths and weaknesses of the approach presented are discussed, as is the question of whether the interpretation is distinct from the spinodal interpretation. What is different from the original spinodal interpretation is that the phase below the apparent instability temperature is still liquid, not solid. The present paper does not purport to have established an accurate account of the molecular behavior responsible for water’s anomalies. Its aim is to call attention to attractive features of the two-state model that deserve further consideration.