Aims and objectives. The aim of this study was to examine the relationship between family social support and loneliness in Turkish patients with cancer. Background. Loneliness is a major problem affecting about 50% of adult cancer patients. Adequate social support may cause a reduced cancer-related mortality in patients with cancer. Design. A cross-sectional, descriptive and correlational design was used. Method. Cancer patients undergoing treatment in the outpatient chemotherapy unit at a university hospital between January-April 2007 were enrolled. After inclusion and exclusion processes, a total of 144 patients with solid cancer comprised the final sample of the study. The Perceived Social Support from Family Scale, the Revised University of California, Los Angeles-Loneliness Scale and a demographic data form were used. Data were analysed by using descriptive statistics, student t-test, one-way variance analysis and Pearson's correlation test. Results. The mean age was 51 center dot 76 (SD 12 center dot 14). Ninety-two patients (63 center dot 9%) were female and most were married. The mean social support score and the mean loneliness score were 15 center dot 92 (SD 3 center dot 22) and 33 center dot 09 (SD 0 center dot 17), respectively. There were significant differences between the mean scores for the marital status (p < 0 center dot 01) and living style (p < 0 center dot 001) characteristics. There was a moderately significant negative correlation between the mean social support scores and the loneliness scores (r = -0 center dot 492, p < 0 center dot 001). The loneliness level of the patients was reduced by increasing social support. Conclusions. The results suggest that the Turkish cancer patients have experienced a relatively low level of loneliness and there is a significant negative correlation between their loneliness scores and their social support scores. Loneliness can be reduced by increasing social support from family members. Relevance to clinical practice. In planning patients' care, nurses should evaluate physiological, psychological and socio-demographic statuses of patients to increase the patients' social support and to decrease their loneliness. Determining and improving family social support of cancer patients should be an essential part of nursing practice. To prevent cancer patients' social isolation, nurses may also encourage family members to enlarge their social support networks.