This study examines the effects of poison put/call covenants on the reoffering yields of corporate bonds issued during 1986 through 1990. The analysis controls for possible biases due to the endogeneity of the decision to issue the bond and the decision to include a poison covenant. The findings indicate that the presence of a single poison call provision has a positive effect on the yield differential, increasing the yield by up to 54 basis points. This is consistent with the managerial entrenchment hypothesis. On the other hand, the inclusion of a poison put provision reduces the yield by 58 to 78 basis points. Furthermore, we find that the imposition of an additional stringent provision to transfer a simple poison put to a super poison put does not significantly decrease the yields further.