Purpose: This study evaluated the efficacy of four methods to prevent chemotherapy-induced oral mucositis (OM) in patients with solid tumors (ST). In addition, the behaviour of OM was investigated in these oncological patients. Materials and Methods: Forty-eight patients, aged 27-84, were randomly allocated to different groups from the first day of chemotherapy (CT), in the following sequence: group 1: intensive oral care programme (IOCP); group 2: 0.12% chlorhexidine mouthrinse; group 3: 0.03% triclosan mouthrinse; group 4: low-level laser therapy (LLLT). Oral mucositis was evaluated on the 7th and 14th days by means of the Oral Mucositis Assessment Scale (OMAS). Results: Thirty-one (64.5%) patients developed OM in the first cycle of CT and the pain was significantly associated with OM severity (p 0.0001). The statistically significantly worst OMAS score was found for the lips and buccal mucosa (p 0.0001). Despite a lack of statistical significance, IOCP and LLLT notably demonstrated potential effects to prevent OM in patients who presented with only oral erythema (75%) and lower peak of severity during the follow up, respectively. Conclusions: Improved oral care awareness is needed in patients undergoing 5'fluorouracil and doxorubicin, mainly to avoid pain caused by oral mucositis. Oral mucositis was more prevalent and aggressive in oral sites exposed to chronic trauma. The IOCP and LLLT approaches showed positive results to prevent oral mucositis and should be further investigated in similar and larger samples. Keywords: cancer chemotherapy agents, low-level laser therapy, oral hygiene, oral mucositis, preventive dentistry