Molecular dynamics simulations of apomyoglobin have been conducted in aqueous solution for 350 ps at 25 degrees C and for 500 ps in two different runs at 85 degrees C. The structures obtained at the higher temperature display properties similar to those of molten globules. Close agreement is obtained between the computed structural models and experimental data on the helical content of both native apomyoglobin and the low-pH unfolding intermediate. The results also suggest explanations for the surprising observations on the effects of mutations at the interface of the A, G, and H helices. Detailed analyses of the final structures and the unfolding pathways at high temperature clearly show that the most stable alpha-helical regions are those in contact with other helices.