A great deal of data has been accumulated on electronic quenching and vibrational energy transfer in vibrational levels v′= 6, 15, 25, 43 and 51 of the B(3Πo+u) state of I2. Analysis of these data permits us to draw a number of conclusions regarding the molecular potential curves and surfaces appropriate to this system. From the quenching data, we learn the shapes of the repulsive curves crossing through the B state curve. Spontaneous predissociation involves the 1Π1u curve, collisioninduced predissociation the 3Πo+u curve, and magnetically induced predissociation the 3Πo–u curve. From details of vibrational and rotational state changes upon collisions with third bodies, the shapes of the I—I—X potential surfaces can be deduced. We have analyzed the collisions by means of numerical integration of classical collision trajectories on these potential surfaces, and compared the predicted results with experimental data. Computer-animated film displays of some of these trajectories can be very helpful in interpreting the dynamics of the collisions.