The aims of this study were to study the patient-, tumour- and treatment-related factors that significantly impact on treatment episode duration for outpatient chemotherapy treatment delivery, and to develop a new measure of outpatient chemotherapy throughput that considers variations in treatment duration compared with the older measures of patients treated per day. A pilot study in our institution randomly measured the duration of outpatient chemotherapy delivery for 266 occasions of service. Patient, tumour and treatment factors were collected and assessed for their impact on treatment duration using multivariate analysis. A new model of outpatient chemotherapy was developed using various modeling processes. Median treatment duration was 90 min. Significant factors that impacted on treatment duration were the chemotherapy regimen, type of infusion, patient age and whether the patients required a community nurse to be organized. A measure was developed (Chemotherapy Basic Treatment Equivalent or CBTE) that considers the variations in treatment duration and showed that although the daily number of patients treated in our department each day remained stable, there were wide fluctuations in workload when variations in treatment duration were considered. A new measure of chemotherapy workload has therefore been proposed although further testing across departments is required. If broadly implemented this could substantially improve resource planning, resource use and patient satisfaction as it considers variations in treatment duration, which is not previously considered in chemotherapy throughput statistics.