Background Latinas in the U.S. are less physically active than non-Latino white women and also report higher levels of diabetes, obesity, and other conditions related to inactivity. Interventions are needed to address disparities in this high-risk group. Purpose To evaluate the efficacy of a culturally adapted, Spanish-language, individually tailored, computer expert system-driven physical activity print-based intervention for adult Latinas. Design RCT. Setting/participants Participants were 266 inactive adult Latinas who participated between 2009 and 2012. Intervention Participants were randomized to one of two treatment arms: a 6-month tailored physical activity intervention condition or wellness contact control. For both conditions, print materials were delivered by mail. Main outcome measures The main outcome measure was change in weekly moderate-to-vigorous physical activity (MVPA) measured by the 7-Day Physical Activity Recall interview, which was administered at baseline and post-intervention (6 months). Participants also wore accelerometers for a week at baseline and follow-up. Analyses were conducted in 2013. Results Increases in minutes/week of MVPA measured by the 7-Day PAR were significantly greater in the intervention group compared to the control group (mean difference=41.36, SE=7.93, p<0.01). This difference was corroborated by accelerometer readings (rho=0.44, p<0.01). Further, results indicate that intervention participants had greater increases in self-efficacy, cognitive processes, and behavioral processes at 3 months compared to control paricipants (p's<0.05). Conclusions The tailored Spanish-language intervention was effective in increasing MVPA among predominantly low-income, less-acculturated Latinas. Such print-based interventions are poised for widespread dissemination, and thus may help address health disparities. © 2013 American Journal of Preventive Medicine.