Casual sex is a new trend in the lives of today’s young adults. Some of the serious consequences that can go along with casual sex are depression, unplanned pregnancy, unsafe abortion, HIV/AIDS and other sexually transmitted diseases. The aim of this study was to determine the magnitude of casual sex experiences and its adverse consequences among college students in Dessie town, north east Ethiopia, 2019. Methods: This study was conducted among college students in Dessie town during April1-30, 2019. Multistage stratified simple random sampling technique was deployed and a total of 617 sample size was determined. Data were collected through self-administered questionnaire. Data were entered Epi data 3.1 and exported to SPSS version 23.0 for analysis. Binary logistic regression was run to identify determinate factors of casual sex and variables whose P value less than 0.25 in binary logistic regression were entered in multiple logistic regression to control the confounding effect of variables. A 95% confidence interval and p-value of < 0.05 was considered to declare the statistically significant. Result: - A total of 610 college students participated in the study which yields 98.9% response rate. Among study participants 44.4% ever had sexual experience and 67.5% start sexual intercourse below age 18 years [need to calculate mean age at sexual debut, males and females respectively]. This study also revealed that 28% practiced casual sex with unknown sexual partner for one night/day and from these 36.3% did not use any protection. Among casual sex practiced 72.6% faced adverse health consequences like STIs, pregnancy, unsafe abortion and from these 39.0% did not seek any medical care. Being female 1.89(1.035-3.462], had not work beyond education 2.63(1.286-5.382], started sexual intercourse <18 years 2.29(1.234-4.251], night club attendance 2.82(1.370-5.824-0.744] and being 1st year student 2.5(1.335-4.767) were determinant factors to casual sex. Conclusion: - Risky casual sex practice among college youths was high. This is alarming to policy makers and local planners to reform strategies to decrease casual sex practice and its consequences among college youths.

Keywords: Casual sex, adverse consequences and college students.