Most attempts to untangle the factors accounting for arms acquisition by nation states rely implicitly or explicitly on the work of Lewis Richardson. However, very few findings from these investigations are durable;one study finds a particular nation state dyad to be involved in an arms race,while the next concludes that this same pair of nations is driven by factors internal to each. The question asked in this paper is: how likely is the true model of a dyadic arms acquisition process to emerge when the Richardson equations are used? This question is investigated by constructing two data sets representing the military capability of a pair of nations-one when an arms race is present and the other when each nation's acquisition of capability is driven by internal factors. These data are then used to estimate the Richardson equations. The conclusion is that in many situations, estimation of the Richardson equations may not uncover the true parameters of the process and may well lead to different conclusions about the same dyadic arms acquisition process.