2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/4657Recent efforts to account for the observed X-ray luminosity - temperature relation of galaxy clusters has led to suggestions that the ICM has an apparent ``entropy floor'' at or above the level of 300 keV cm^2. Here, we propose new tests based on the thermal Sunyaev-Zeldovich effect and on the cluster gas mass - temperature trend (from X-ray data) to probe the level of excess entropy in the ICM. We show that these new tests lend further support to the case for a high entropy floor in massive clusters.2 pages, 2 figures, to appear in `Galaxy Evolution: Theory and Observations', Eds. V. Avila-Reese, C. Firmani, C. Frenk, & C. Allen, RevMexAA SC (2002)Astrophysicstext