Sustained high rate of inflation has led to the creation of debt instruments with variable interest rate. The availability of these debt instruments presents management with the problem of the choice of the optimal debt portfolio. This paper deals with this problem assuming a given, and optimal, debt to equity ratio. Given expected monetary value maximization, an efficient frontier is derived in terms of the expected net income and probability of bankruptcy, where net income is defined as operating income minus debt repayment. This efficient frontier is shown to be also mean-variance efficient. It is also shown that in most cases the optimal debt portfolio includes more than one debt instrument. In other words, the firm will avoid the policy of minimizing the expected cost of its debt repayments or the policy of minimizing the costs of bankruptcy. The optimal solution itself is affected by market variables like the relative expected cost of different debt instruments and by firm specific variables like the variability of its operating income stream, and the covariance between the operating income and the debt repayments.