This research aimed to 1) study the effectiveness of Computer-Assisted Instruction on the Computer Systems Information Technology Subject follow the prescribed criterion 75/75 level 2) compare the learning achievement of students taught by Computer-Assisted Instruction to traditional method and 3) study the students satisfaction through Computer-Assisted Instruction. The sample groups were one hundred Mathayomsuksa I students of Bangbowitthayakhom School, Bangbo district, Samuthprakarn province in the second semester of 2009 academic year. The instruments of this research were Computer-Assisted Instruction and traditional method lesson plans, achievement test, and students satisfaction evaluation questionnaire. The statistics used are mean, standard divination, and t-test.
	The findings were as follows :
	1.  Computer - Assisted Instruction variable were 80.25/82.40, which met the prescribed criterion 75/75 level.
	2.  The significant difference between the  mean  score of the experimental group and that of the control group was found at a .01 level. 
	3.  The students satisfaction about Computer - Assisted Instruction was 4.53  which  was indicated  at  a  high level.
