This study examined the prevalence, stability, and fluidity of sexual orientation as well as the prevalence of gender discontent. From a community sample (i.e., all adolescents of the age cohort were invited), this study analyzed data from 1513 adolescents (50.5% females), who replied to questions about sexual attraction on at least one of three occasions (age 14: n = 623; age 15: n = 1322; and age 17: n = 949). Sexual orientation was operationalized from the attraction pattern and shifts in that pattern were analyzed longitudinally. Gender discontent was measured only once, at 17 years. Various types of sexual orientation were found, including homo-, bi-, a/non-, and heterosexual (on all three occasions) alongside gender discontent (at age 17). The results revealed the fluidity of sexual orientation during adolescence, including the decrease of nonsexuality from 14 to 17 years in both girls (from 10.2 to 2.1%) and boys (from 9.4 to 3.4%) shifting to stronger sexual attractions, primarily heterosexuality (girls from 69.4 to 74.8%; boys from 83.1 to 88.5%). Bisexuality emerged as more prevalent among girls than boys (18.2 vs. 4.5%). Notably, stability in a homosexual pattern was lower than other sexual orientations, since few remained in that same group from 15 to 17 years old (girls 17.6%, boys 29.4%), suggesting frequent shifts to and from other groups. Gender discontent was endorsed by 1.7% with about the same number of both genders and an array of sexual orientations was shown. These findings emphasize the nuanced developmental trajectories that adolescents navigate while forming their sexual identities.