Bioassays were conducted on nine chemicals using one week old larvae and one month old fingerling striped bass, Marone saxatilis (Walbaum), as the test species. The chemicals tested were potassium permanganate, potassium dichromate, copper sulfate, Dylox, ethyl and methyl parathion, Karmex, butyl ester of 2, 4-D and HTH. Tests were conducted at 70° Fahrenheit in glass containers using reconstituted water as the diluent. The fingerlings were much more tolerant to Karmex, potassium dichromate, potassium permanganate and butyl ester of 2, 4-D than were the larvae. A higher concentration of ethyl parathion, methyl parathion, HTH, copper sulfate or Dylox was required to kill the larvae than the fingerlings.