My name is Nick. I am a doctor and i would appreciate any of your help in the above problem. Recently, on purpose to delineate/propose a specific risc factor for a specific disease i proceeded in a binary logistic regression on SPSS. My model was characterized by one categorical (dichotomous) variable and 5 independent also categorical (and also dichotomous) variable. My model has been worked fine, i had a very big general population (2300 patients), a good one as regards my dependent variable (51), it seems that i managed to correlate my dependent variable with the one independent i wanted from the beggining, but in a conversation that i had with my supervisor proffessor we noticed one problem, and he proposed me something more that i really didn't understand so well. So regarding the problem, even we noticed that our data gave us a very good OR concerning the correlation between the 2 diseases that we thought from the beggining to be related, we noticed that 2 of our independent variables had negative OR. These obviously happened because we had few patients that combined each of the 2 independent diseases (2 and 3 respectively) with the dependent disease. So because our aim is to present only the positive relation with the disease that we wanted and not negative correlation of the dependent disease with the other 2 aforementioned (cause such an idea is wrong either way, or at least we don't want to show something like that) i decided to shorten these 2 categories to 1 (patients that have either the one or the other disease) with the hope in a new model i have a positive OR. My problem mainly has to do with another thing too. My professor told me that he would prefer a multivariate model and not a univariate like mine cause multivariate models have higher strengh. But i can not imagine how to do something like that. How can you proceed to multivariate logistic regression and not binary when you have a dichotomous dependent variable and 3 categorical (again dichotomous) variables to SPSS or generally eveywhere??? Please help...Thank you in advance