Effects of temperature and dose-size on infectivity and reproduction of Korean entomopathogenic nematode, Steinernema longicaudum Gongju strain were examined. The greater wax mea Galleria mellonella larvae were exposed to 5, 10, 20, 40, 80, and 160 infective juveniles/larva in $60{ imes}15$ mm petri dishes and kept in $13^{circ}C$, $18^{circ}C$, $24^{circ}C$, and $30^{circ}C$ incubators. Each petri dish contained one larva weighed from 180 to 200 mg. Infectivity was observed everyday for 14 days and reproduction for 30 days. The infectivity of S. longicaudum was more influenced by temperature than by dose-size. Mortalities by S. longicaudum were lower at $13^{circ}C$ at all concentrations but higher at $24^{circ}C$ and $30^{circ}C$ even at lower concentrations, 5 or 10 infective juveniles/larva. Lethal time was also shorter with increasing temperature and dosages. All host larvae died at $24^{circ}C$ and $30^{circ}C$ in 2 days at the rate of 160 infective juveniles per host while 83.3% of tested larvae died at $24^{circ}C$ in 10 days and 90% at $30^{circ}C$ in 6 days at the rate of 5 infective juveniles. Reproduction was also better with increasing temperature and dosages. The highest number of progenies was obtained at $30^{circ}C$ in 6 days at the rate of 80 infective juveniles. However, progenies were not produced from cadavers at $13^{circ}C$. Reproductive period was the shortest at $30^{circ}C$ of all temperatures by 6 to 9 days. The results indicated that optimum temperatures for infectivity was $24^{circ}C$ and $30^{circ}C$ for reproduction.