Despite the prevalence of computing in all aspects of society, some computer systems may not be fully accepted by their intended users or become underutilized. Thus, acceptance and use of information technologies remain a paramount issue in information systems (IS) research and practice. Extending previous research by integrating computer self-efficacy and perceived system complexity as external variables to the technology acceptance model (TAM), this study examines the direct and indirect effects of these two factors on system acceptance and use. The results indicated that computer self-efficacy and system complexity had significant direct effects on perceived usefulness and perceived ease of use as well as indirect effects on attitude and behavioral intention. However, the effect of perceived ease of use on attitude was stronger than that of perceived usefulness. In turn, attitude demonstrated a non-significant impact on behavioral intention. These findings highlight several implications for research and practice.