Ecological Momentary Assessment (EMA) was used to investigate associations between, and variations in, ejaculatory control and ejaculation latency time (ELT) over repeated measurements of sexual activities. Differences between measures recorded in partnered or non-partnered settings were also investigated. The sample consisted of 21 male Finns aged 18 years or above, contributing a total of 158 reports of partnered and non-partnered sexual activities over a six-week period. In the context of non-partnered sexual activities, after controlling for within-subjects dependence, ELTs between events were predictive of one another, but ELT did not predict ejaculatory control when measured simultaneously, nor at subsequent events. Also, ejaculatory control could not predict simultaneously measured ELT or ejaculatory control at subsequent events. During partnered sexual activities, both ejaculatory control and ELT could be accurately predicted by observing ejaculatory control at prior events. In this context, ejaculatory control could also reliably predict simultaneously measured ELT. ELT or ejaculatory control during partnered sexual activity could not be predicted by observing ELT at prior events. Between-event correlations were generally low, indicating considerable variation in ejaculatory functioning over time. EMA is a thrifty assessment method for studying variations in ejaculatory function, and is likely suitable for studying sexual dysfunctions in general.