An essential element of a plaintiff's cause of action for negligence is a reasonable connection between a defendant's act or omission and the damage suffered by the plaintiff. Thus, causation has been an area of concern in recent years in the formulation of standard jury instructions. At present, the Supreme Court of Florida Committee on Standard Jury Instructions is reevaluating casusation intructions, focusing on the issue of whether the instructions should include the substantial factor test of cause or continue to apply the more common 'but for' test. Under the 'but for' test, the defendant's conduct is a cause of the plaintiff's injury if the injury would not have occurred but for the conduct of the defendant. Under the substantial factor test, the actor's neligent conduct is legal cause of harm to another if his conduct is a substantial factor in bringing about the harm, and there is no rule of law relieving the actor from liability because of the manner in which his negligence has resulted in the harm. Both tests achieve the same results in the majority of negligence situations. However, in cases involving concurring, alternative, and successive causes where each cause is sufficient to produce the harm, the 'but for' test fails to provide the result that justice requires in determinations of cause in fact. In those cases, the substantial factor test has proven to be superior and more reliable. Therefore, the conflict as to which test to adopt in standard jury instructions should be resolved in favor of the substantial factor test. The proposed instruction, notes, and 229 footnotes are provided in the article.