Sentana OM, Haryati S, Mariyah Y. 2011. Effects of anthelminthic of ethanol extract of basil (Ocimum americanum) leaf against Ascaris suum death in vitro. Biofarmasi 9: 1-6. This research aimed to examine the relationship between the ethanol extract of basil leaf against Ascaris suum mortality rate in vitro. This study was a laboratory experiment with a research design of the post-test with controlled group design. The samples were Ascaris suum Goeze that still actively moved and obtained from pig intestines. The sampling technique used was a purposive sampling by equating the type and the length of worms, and it did not distinguished for the sex of worms. The subjects were divided into five groups, each group consisted of 5 worms and repeated in 6 times. The control group contained 25 mL of physiological saline solution and 25 mL pyrantel pamoate 5 mg/mL. Three other groups contained basil leaves extracts consisted of various concentrations, i.e. 30%, 40% and 50%. The number of dead worms was counted every 2 hours until all the worms in the group died. The data were analyzed by using a linear regression analysis and a probit analysis. Simple linear regression statistical test showed a significance correlation at 0.000 with 0.837 correlation coefficient was negative, R square 0.701, in which the significant correlation <0.05 or the value of 37.565 with a significance of means, there was a negative relationship between the length of time of death of worms with large concentrations of basil extract. Analysis using a probit analysis obtained LC50 at a concentration of 40% and LT50 at a concentration of 40% was 2 hours. The ethanol extract of basil leaf could affect the death of A. suum in vitro with LC50 at a concentration of 40% and LT50 at a concentration of 40% was 2 hours.