The complexity of a pharmacological treatment can lead to a lack of adherence to the proposed treatment and consequently damage the recovery of the patient's health. The objective was to evaluate the complexity of the treatment regimen used by elderly patients attended in Basic Pharmacy of Santa Cruz do Sul, RS, and associated factors. I was done a cross-sectional study with data collection in the period from August to September 2014, through individual interviews with a semi-structured questionnaire containing sociodemographic variables, behavioral, health and pharmacotherapy variables. The therapeutic complexity index (TCI) was obtained by direct measurement of the necessary actions to administer the medicine. 300 elderly were interviewed; 76.7% were female, 70% aged 60-69 (± 6) years, and 77% had physician consultation in the last six months. The most cited diseases were hypertension (44.3%), depression (43%), high cholesterol (32%), diabetes (21%) and osteoporosis (20.7%). In the 15 days preceding the interview, the interviewers took a total of 1088 medicines (mean = 3.6 (± 1.74)). The TCI ranged from 1 to 30 (mean = 6.67 (± 5.35)) with statistically significant association (p < 0.05) with the female, referred diseases (diabetes, high cholesterol, osteoporosis, bronchitis, hypertension), take several medications at the same time and non-adherence to treatment. The evaluation of the complexity of pharmacotherapy is necessary and important for the restoration and maintenance of elderly's health. Simplifying treatment regimens can improve medication adherence and benefit on the outcome of therapy, allowing an understanding and a more accurate approximation of the elderly with their treatment.Keywords: elderly; pharmacotherapy; medication adherence RESUMO A complexidade de um tratamento farmacológico pode acarretar falta de adesão ao tratamento proposto e, consequentemente, prejuízos na recuperação da saúde do paciente. O objetivo foi avaliar a complexidade do regime terapêutico utilizado pelos idosos atendidos na Farmácia Básica de Santa Cruz do Sul -RS e os fatores associados. Foi feito um estudo transversal, com coleta de dados no período de Agosto a Setembro de 2014, por meio de entrevista individual com questionário semiestruturado contendo variáveis sociodemográficas, comportamentais, de saúde e da farmacoterapia. O índice de complexidade terapêutico (ICT) foi obtido por meio de medida direta das ações necessárias para administrar o medicamento. Foram entrevistados 300 idosos, sendo que 76,7% do sexo feminino, 70% tinham idade de 60 a 69 (± 6) anos e 77% realizaram consulta médica nos últimos seis meses. Dentre as doenças referidas destacaram-se hipertensão (44,3%), depressão (43%), colesterol elevado (32%), diabetes (21%) e osteoporose (20,7%). Nos 15 dias anteriores à entrevista, foram utilizados 1088 medicamentos pelos idosos entrevistados [média = 3,6 (± 1,74)]. O ICT variou de 1 a 30 [(média = 6,67 (± 5,35)], apresentando associação estatisticamente significativa (p < 0,05) com o sexo feminino...