Okadaic acid and the dinophysis toxins (DTX-1-4) are primary agents responsible for diarrhetic shellfish poisoning (DSP) and maybe implicated as one of the many toxins resulting in ciguatera fish poisoning (CFP). Cultures of seven planktonic Prorocentrum species and nine benthic-epiphytic Prorocentrum species were analyzed for the production of cytotoxic compounds and protein phosphatase inhibition activity. Scanning electron microscopy positively identified all cultures. Cultures that showed phosphatase inhibition activity were analyzed for okadaic acid and the dinophysis toxins using LC-MS/MS. All seven species of planktonic Prorocentrum (P. micans, P. triestinium, P. dentatum, P. minimum, P. compressum, P. balticum and P. areabium) displayed no protein phosphatase activity. Of these species only a newly described species P. areabianum showed activity to the cytotoxic assay. Four of the nine benthic-epiphytic Prorocentrum species (P. lima, P. hoffmannianum, P. belizeanum, and P. faustiae) displayed protein phosphatase activity and only one (P. mexicanum) displayed cytotoxic activity. Subsequent analysis by LC-MS/MS shows the production of okadaic acid by P. lima, P. hoffmannianum, P. belizeanum and P. faustiae. However, only P. lima and P. belizeanum were shown to produce dinophysis toxins. Cultures of the benthic-epiphytic species P. emarginantum, P. areanarium, P. elegans, and P. norrisianum were found to be non-toxic.