摘要：The study was conducted to study toxicity and accumulation levels of trichlorofon in Nile tilapia ( Oreochromis sp.) in weight of 2.54±0.79 g. Experiment was diveded into three steps, i.e., (1) determination of toxicity range for 48 hours, (2) devinitive test for 96 hours, and (3) bioaccumulation test for 96 hours. Experiment was performed using aquaria (volume 10 liter) with semi-static system. Data was analyzed descriptively and probit test. The results of study indicated that Nile tilapia (8.33%) died after exposuring with trichlorofon 8 ppm for 24 hours, and all fish died when they were exposured with trichlorofon 50 ppm for 18 hours. LC 50 value at 96 hours was 8.52 ppm, while safe concentration levels was 0.43 ppm. Accumulation rate of tricholorofon in the body Nile tilapia was 0.11% per day. Keywords: toxicity, trichlorfon, Nile tilapia, Oreochromis sp. ABSTRAK Penelitian dilakukan untuk mengetahui tingkat toksisitas dan akumulasi insektisida triklorfon pada ikan nila ( Oreochromis sp.) dengan bobot 2,54±0,79 g. Percobaan dilakukan dalam tiga tahap, yaitu uji penentuan kisaran selama 48 jam, uji definitif selama 96 jam dan studi bioakumulasi selama 96 jam. Percobaan menggunakan akuarium kaca volume 10 liter dengan sistem semi statik. Data dianalisis secara deskriptif dan analisis probit. Hasil penelitian menunjukkan bahwa ikan nila mulai mati setelah diberikan triklorfon 8 ppm selama 24 jam, and semua ikan mati dengan pemberian triklorofon 50 ppm selama 18 jam. Nilai LC 50 96 jam sebesar 8,52 ppm, sementara tingkat konsentrasi aman sebesar 0,43 ppm. Terjadi peningkatan konsentrasi residu dalam tubuh ikan nila dengan laju penyerapan harian 0,11%. Kata kunci: toksisitas, triklorfon, ikan nila, Oreochromis sp.
