The consequences of assuming the third-generation Yukawa couplings are all large and comparable are studied in the context of the minimal supersymmetric extension of the standard model. General aspects of the renormalization group (RG) evolution of the parameters, theoretical constraints needed to ensure proper electroweak symmetry breaking, and experimental and cosmological bounds on low-energy parameters are presented. We also present complete and exact semianalytic solutions to the one-loop RG equations. Focusing on SU(5) or SO(10) unification, we analyse the relationship between the top and bottom masses and the superspectrum, and the phenomenological implications of the grand unified theory (GUT) conditions on scalar masses. Future experimental measurements of the superspectrum and of the strong coupling will distinguish between various GUT-scale scenarios. And if present experimental knowledge is to be accounted for most naturally, a particular set of predictions is singled out.