The suicide rate & the death rate for undetermined causes were negatively associated over time from 1968 to 1990 in the USA, suggesting that these undetermined deaths may include a fair proportion of suicides. In contrast, there was no association between suicide & undetermined death rates over the states in 1980. While the undetermined death rate may account in part for time-series changes in the suicide rate since 1968, it cannot account for regional variations over the 48 contiguous states.