A study was conducted in the Vector Control Research Station laboratory in Salatiga and in ponds belongs to inhabitants of Sukutukan village, Wulanggitang Sub District, East Flores Regency. These ponds were found to be an area of breeding sites for Anopheles barbirostris. This study was conducted from August - September 1992 to determine the efficacy of Bacillus thuringiensis H-14 against An. barbirostris larvae in the laboratory and in the field. The effect of B. thuringiensis H-14 (Teknar SC) toward An. barbirostris larvae in the laboratory was conducted according to WHO guidelines to assess the lethal concentrations (LC50 and LC90) which were calculated through the probit analysis. Laboratory tests of B. thuringiensis H-14 (Teknar SC) showed that after 24 hours of exposure, concentrations of 0.9893 and 11.2906 ppm caused approximately 50% and 90% mortality, respectively, for early fourth-instar larvae of An. barbirostris. After 48 hours of exposure, the LC50 and LC90 values calculated for early fourth-instar larvae of An. barbirostris were 0.1499 and 3.3396 ppm, respectively. Test of standard B. thuringiensis H-14 (IPS 82) concentrations required 110 to 522 times lower than Teknar SC, the LC50 and LC90 values for An. barbirostris larvae were estimated as 0.0021 and 0.1024 ppm, respectively, after 24 hours of exposure, while after 48 hours of exposure, the LC50 and LC90 values were 0.0012 and 0.0064 ppm respectively. In the field tests, Teknar SC at dosages of 0.6, 0.75, 1.0 and 1.2 l/Ha caused 84.25%, 84.91%, 91.38% and 84.58% reduction in 1-11 instar An. barbirostris larvae, respectively, while in III-IV instar larvae it was 89.15%, 90.62%, 82.99% and 92.0% respectively after 24 hours exposure. No significant difference in percent reduction between dosages used (p>0.05). Six days after application of Teknar SC, reduction of larval population density were very low with very little or negative reduction.