Using a combination of Monte Carlo techniques, we locate the liquid-vapor critical point of adhesive hard spheres. We find that the critical point lies deep inside the gel region of the phase diagram. The (reduced) critical temperature and density are τc = 0.1133 ± 0.0005 and ρc = 0.508 ± 0.01. We compare these results with the available theoretical predictions. Using a finite-size scaling analysis, we verify that the critical behavior of the adhesive hard sphere model is consistent with that of the 3D Ising universality class.PACS numbers: 61.20.Ja, 64.70.Ja The structure of a simple liquid is well described by that of a system of hard spheres at the same effective density. To a good approximation, the effect of attractive interactions on the liquid structure can be ignored. This feature of simple liquids is implicit in the Van der Waals theory for the liquid-vapor transition, and has been made explicit in the highly successful thermodynamic perturbation theories for simple liquids [1]. The perturbation approach becomes exact as the range of the attractive interaction tends to infinity while its integrated strength remains constant [3]. We refer to this limit as the 'Van der Waals' (VDW) limit [2]. Conversely, as the attractive forces become shorter-ranged and stronger, the perturbation approach is likely to break down. Fluids with strong, short-ranged attraction (so-called 'energetic' fluids [4]) are of growing importance in the area of complex liquids. For example, short-range attractions are thought to be responsible for the transition from a 'repulsive' to an 'attractive' glass [4], which has recently been observed experimentally in PMMA (polymethylmethacrylate) dispersions [6].In this Letter, we consider a model system that can be considered as the prototypical energetic fluid: a fluid of adhesive hard spheres (AHS). Introduced in 1968 [7], the AHS model is a reference system for particles with short range attractions. The pair potential consists of an impenetrable core plus a surface adhesion term that favors configurations where spheres are in contact. At larger separations, there is no interaction. The AHS model can be considered as the 'anti Van der Waals' limit.Baxter showed [7] that the Percus-Yevick (PY) equation can be solved analytically for adhesive hard spheres. In fact, Baxter's solution is often used to to analyze experimental results for systems as diverse as silica suspensions [8], copolymer micelles [9], and the fluid phase of lysozyme [10].One important feature of the AHS model is that its phase diagram contains a liquid-vapor coexistence region [11]. The PY equation offers different routes to estimate the location of the liquid-vapor critical point. However, the 'compressibility route' [7] and the 'energy route' [12] lead to estimates for the critical temperature that differ by some 20%, while the estimates for the critical density differ by almost a factor of three. For the analysis of experimental data, it is important to know the location of the critical point more accurately. The ...