Controller:
public class Sample{ public String selectedOption { get; set; } public Sample() { selectedOption = 'No'; } }
Visualforce Page:
<apex:page controller="Sample"> <apex:form id="form"> <apex:selectRadio value="{!selectedOption}"> <apex:actionSupport event="onchange" rerender="form" /> <apex:selectOption itemValue="Yes" itemLabel="Yes" /> <apex:selectOption itemValue="No" itemLabel="No" /> </apex:selectRadio> <apex:inputText rendered="{!selectedOption='Yes'}" /> </apex:form> </apex:page>