Four hundred and fifty adults (mean age 34 years; 55 percent males) from northwestern Ethiopia were interviewed to explore their causal beliefs about, perceived importance of various treatments for, and attitudes towards, six mental and three physical illnesses. Principal components analysis identified four meaningful illness causal belief dimensions: Psychosocial Stressors, Supernatural Retribution, Biomedical Defects, and Socio-Environmental Deprivation. Psychosocial Stressors and Supernatural Retribution were rated more important causes of mental than physical illnesses. Prayer and home/family care were suggested more strongly for treating mental than physical illnesses. Systematic associations were found between causal beliefs, treatment beliefs, and attitudes towards patients. Respondents' educational level was negatively related with traditional beliefs and positively related with favorable attitudes towards patients. It is concluded that causal beliefs, perceived importance of treatments, and attitude towards patients among northwestern Ethiopians are meaningfully interrelated. Implications for health services and research are discussed.