An experimental study through a randomized clinical trial, without blinding (for participants and the research team), with a control group (not subject to intervention) and an intervention group (subject to two text messages, an automated non-human call or a call made by the administrative assistant, and a phone call made by a physician).

Inclusion Criteria:

Participants must be registered in the ULS of

Barcelos/Esposende and meet the following criteria:

1. Age between 50 and 74 years.
2. No symptoms such as weight loss in the last 6 months or gastrointestinal symptoms.
3. No prior diagnosis of CRC.
4. No diagnosis of inflammatory bowel disease (ulcerative colitis or Crohn's disease).
5. No family history of CRC in first- and second-degree relatives diagnosed before age 60.
6. No prior fecal occult blood test (FOBT) in the 11 months before receiving the collection kit or no prior sigmoidoscopy or colonoscopy in the last 24 months.

Exclusion Criteria:

1. Participants who did not receive the screening kit at home.
2. Participants without a phone number.
3. Participants who do not answer the phone or refuse to participate in the study.
4. Participants unable to consent or perform the screening due to physical, mental, or other conditions that seriously impair comprehension.

We plan to share de-identified individual participant data (IPD) that underlie the results reported in this study, including text, tables, and figures. The data will be made available beginning six months after publication and will remain accessible for a period of five years. Access will be granted to researchers who submit a methodologically sound proposal, subject to approval by the study team. Along with the IPD, supporting documents such as the study protocol, statistical analysis plan, and informed consent form will also be available. Requests for data access should be directed to Marina Pinheiro, MD, PhD email: mpinheiro@icbas.up.pt.